Teacher - is the small bevel gear tightened right down and straight? I gave mine a little tap before screwing them on to make sure they were fully on the shaft. My gear cases and diffs are perfect with the standard shimming.
komkit - no 6 deg blocks yet - car has 5 degrees caster as standard (4 degree block, 1 degree kickup). You could use the supplied shims to increase/decrease kickup, to get more/less caster (changing kickup has a different effect to simply changing caster though)