if i were to wedge the front of my truck (lets say with the khiro hard wedge risers), how would I know what thickness riser I would need at the back truck to equalize the height to the front? No one I know seems to be able to gimme a straight answer :P i'm guessing the slalom guys out there will know best about this.
I've never bothered to get too accurate with this. I just have a good look at the wedge, and use a riser with a height about halfway between the thick end and the thin end of the wedge. If you're out a millimetre or two I don't think it'll matter. In slalom you often use a completely different truck in the rear to in the front, so the heights are gonna be off anyway. Some people deliberately run a lower rear truck setup, so you may as well experiment and see what works for you.
if your using it for freeriding it may be perferable to be a touch on the generous side with how big you go on the back as forward rake is not a bad thing but tends to be abit off putting if its the other way around