The smaller they get the faster they will be. At big events we cut all of our hand out motors to .285 even before we run them the first time. As the comm gets smaller you get more brush overlap and more rpm.
I dont do this at club races though as you kill about 2/3 of the motors life.
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series