Hi 2-Bad,

Standard servos are fast enough for M05.

Plastic steering rack ok, except it has to be build carefully to avoid binding.

My experience with hopping is with the SWB and the LWB. The Mid wheelbase seems to be best compromise.

Straight line wander can be from a tight diff or lack of rear toe in.

Here's a good battle between my daughter's M05 (pink) and M06 (SWB, orange S800). M05 is with standard servo, S-grip tires, M05 ball diff, plastic steering rack, 2 deg rear toe hubs, zero front toe, 5mm ride height, Tamiya Lightly tuned motor and 2400 NiCad per Tamiya Asia Cup rules. M05 ball diff built normally like a TC diff, not cranked tight.

hth.