Review: The Göldo BackBox

The instructions that come with the BackBox are in German. Rockinger has an English translation of them on their site but, even then, they're not very helpful. You might have better luck with the following instructions. This is the tried-and-true method that I've developed after installing 3 BackBoxes and an ESP Arming Adjuster. It should work for either of those or an Ibanez BackStop. If you do it for an Ibanez, just do every step twice, once for each of the mechanisms:

Locate the two knurled knobs. One knob (the one on the outside of the frame) adjusts the position of the "pusher" (which will be contacting the tremolo). The other knob is on the "inside" (between the ends of the frame) adjusts the pre-tension in the spring. Become familiar with which is which and how they work.
Adjust the positioning knob so that the threaded rod is just flush with the knob (ie, just before the threaded rod would start to poke out the end if you retracted the pusher any further back into the frame).
If you have to remove springs to fit the BackBox in the cavity, then do so (and consider buying some stronger springs from your local guitar store... especially if you have a 7-string guitar).
Don't install the BackBox, yet.
Decide what brand of strings you want to use for a long time. If you change the sizes or even the brand/model (because the metal compositions vary amongst manufacturers) of your strings, the tension required to hold the trem in a certain position will change (as will the intonation of your guitar), and you'll have to do all of the following steps again. So, choose a brand/model of string and stick with it.

(Also, from here on, pay special attention to when I say springs and when I say strings. There's only one letter difference between these two, and you might have to start all over if you adjust the wrong one at the wrong time)
Decide where you want the rest position of your trem to be once this is all done. Install the whammy bar and look at the whole thing from the side and make sure that you know where you want the trem to float when it's at rest. Loosen the springs by unscrewing the spring-claw screws a bit and also tighten some of your wound strings a little until the tremolo is pulled well forward of this rest position.
Now, find a block, chunk of wood, roll of coins, stack of playing cards (actually, playing cards would probably be perfect for this, since you can adjust the thickness by adding/removing individual cards. You might need to staple them all together when you know how many you need, though, since they might slip out later and you could lose one and the whole process would go straight to hell), etc. to block the tremolo there. You do this by inserting your spacer block between the tremolo block (the thing that the springs... not strings... springs... connect to and which extends through the body of the guitar)... between that and the back (ie, away from the neck) of the trem-block cavity. This keeps the trem from pivoting any further forward. You'll have to pull up/back on the whammy bar to make room for the block but, once you do, you should be able to let go and the block will be held in there by the string tension.

Now, let's examine where we're at. The strings are not yet at their proper pitch, the springs are set too loose, and the block is keeping the tremolo from pitching any further forward from our desired rest position.
Tune the strings up to full pitch (and, if they're new strings, probably let them sit for a day as they stretch and you retune them up to pitch)

At this point, the trem is in it's desired rest position and the strings are up to pitch. The only problem now is that the springs are too loose and so our spacer block is required to hold the trem in place. So, we just need to get the springs to start bearing all of the load.
Gradually tighten the screws for the spring-claw to stretch the springs. As you do this, test how easy it is to wiggle the spacer block. As you get closer and closer, the spacer block should get easier and easier to wiggle until it isn't being pressed on by the trem-block at all and either falls out or you can easily slip it out.

At this point, the trem is in the right rest position, the strings are very close to proper pitch (if it's a little high, then loosen the springs just a smidge), and the springs are holding this on their own. Perfect! Oh, wait... we forgot to put the BackBox in!
Now... install the BackBox in a position so that the felt almost touches the trem-block (when I say "almost"... a sixteenth of an inch or a couple of millimeters is fine. Closer is probably better, but don't worry too much about getting it "within the width of a human hair" or anything). You should drill a little pilot-hole for the screws (DO NOT DRILL ALL THE WAY THROUGH AND OUT THE FRONT OF YOUR GUITAR! Hold one of the screws up to the drill bit you're going to use and put a piece of tape on the drill to let you know how deep to go), and you may have to drive one of the screws in at an angle. This is fine. Just make sure that the BackBox is securely fastened and doesn't wiggle when you push or pull on it.

UPDATE: Someone who bought a BackBox from me had this handy tip for avoiding drilling at an angle. It's a little more work, though. The reason you'd need to drive that one screw at an angle is because the whole plunger/spring mechanism is in the way. However, what you can do is take all of that apart so that you only have the aluminum base. Then, ONLY screw in that one troublesome screw (the one closest to the tremolo block). The reason you don't screw in the other screw, yet, is because you're going to need to swivel the BackBox base around a little in order to put the "guts" back into it. In fact it may not even be possible without temporarily removing some of your trem springs. So, put the guts of the BackBox back in and then install the remaining screw.
Now, position the pusher properly. It is extended too far if you see the BackBox move when you pitch the tremolo forward (ie, to dive the strings). It is retracted too far back if you are able to hear the strings go up in pitch much if you press on the back (where the fine tuners are) lightly. In other words, we want the BackBox to not be part of the equation when you're rocking your tremolo forward (diving strings), but we want it to be resisting even the slightest movement back (ie, raising the strings). Take some time getting this just right, because it really affects how things will turn out. Also, it helps to use a chromatic tuner to see just how much your strings are going up when you rest your palm on the trem. You probably will never get it perfect. If you can get it so that you can't hear any rise in pitch, then you're there.

At this point, the BackBox is resisting the tremolo from coming back (if you rested your palm on the fine tuners or broke a string), but not from going forward (if you bent a string). We want to make it start resisting in both ways.
Start tightening the screws for the spring claw some more. This is going to cause the springs to be applying more force than is needed (but the BackBox will be keeping the tremolo from moving). This extra force will only come into play when you try to bend a string or rock the trem forward. The easiest way I've found to set this right is to play some string (like the high-E) while you bend another (like the B) as much as you anticipate ever needing to bend. You don't have to play the bent string. The bend is just to add tension on the trem. Play an unbent string and bend an unplayed string. At first, you'll hear the played string fall in pitch. So, tighten the screws in the spring claw and try again. Keep doing this until the unbent, the played string doesn't fall in pitch as you bend. KEEP IN MIND, however, that, as you're tightening the springs, the BackBox might start moving, as the increase in spring tension overcomes the pre-load in the BackBox's spring. If this happens, pre-load the BackBox spring more (with the middle knurled knob).

In short, we're trying to tighten the regular springs so that they're able to absorb any increase in string tension we anticipate, and the BackBox (with its preloaded spring) has the job of keeping the tremolo from rocking back (without you pulling on the whammy bar). But the more you tighten the springs, the more you'll need to pre-load the BackBox.

So, now, you should have the strings pretty close to the right pitch, the trem is in the proper rest position, and the trem doesn't dive when you bend a string. The last step is to make sure that the trem doesn't rock back if you rest your hand on the fine tuners.
This last part is comparatively easy. Play a string and rest your palm on the fine tuners. If the pitch of the string goes up, then you need to increase the pre-load of the BackBox yet a little more. Keep doing this until the resistance to rocking back is to your liking. If you want the trem to stay perfectly in tune when you break a string, you may have to pre-load the BackBox by quite a bit. You could test a string breakage by loosening the E string until it's slack and seeing if the pitch of the other strings went up.