One aditional note....
I noticed when I shimmed my m spec buggy that the bulkhead lets the diff bearings move too much so the simple fix is to drop one drop of superglue on the inside of the bulkhead cover where the bearing rides and let it even out and dry, then when you screw the cover down it will hold the bearings tighter and keep ur mesh where you set it longer....
The easiest way to check mesh is to hold the center axle and rock the outdrives back and forth when the car is assembled. If there is more than a tiny ammount of play take the diff out and shim it a bit closer, and take ur time doing it. I've ofund if you use a shim on the inside of the outer bearing and the bulkhead you will get the pinion locked in without front to back play...basically put a med thin diff shim in the bulkhead then the outer bearing where the center cvd rides...
Also if you put a small shim on the diff gear side, and the diff case side before you put the bearing on it your adjustment will stay put longer than using alot of shims that slide over the outdrive bearings.....those should be for fine tuning....