GreaseMonkey -- Your results sound similar to what we've seen locally. The bonded rotor versions of the 13.5 have very different performance characteristics (more torque, less RPM), but that is just "gearing". The lap times are essentially the same (with BONDED rotor). My best run with a Co27 was 0.1 sec. faster than my best run with a bonded rotor 13.5...
The racing has been very close and fun, with zero problems -- the race results always come down to setup and driving consistency...
We have NOT tried LiPo yet...
"If you cannot win, make the one ahead of you break the record."
Biff Racing Team #420 (Ah... The "good old days"...)
The local indoor Offroad Track: The RC Race Barn
TLR22-3.0, TLR22T-2.0, TLR22SCT-1.0