We ran nsr f1 for the first time as a class at my club this Tuesday on 13.3 volts see pics of track at ssrc website with standard nsr 21.4 motor. others had a few deslots due to incorrect controller settings I had no such problems and would easily have run on 13.8 might just be me but they are a docile motor,plenty of torque,but no real speed,but then again my modified cars are all powered buy motors over 35k as to slot god just a bit of fun having seen the slot king type Handel as in Joel's profile I thought people put them in themselves I didn't realize they were added automatic buy the site software.so don't take it personally guys .but as they say if the cap fits. I might change it soon though had that for ages.joel don't put the 38 back in as their to heavy on the tyres which will never be a problem with 17 k but to get back to the original topic any of the motors mentioned will be ok if that's the specs you have to use
Cheers Alan