About this 3D model

I'm about to build up the great Rostock concept: http://www.thingiverse.com/thing:17175 as T2,5 timing Belts are much more available for me than the GT2, I was looking for a pulley with a matched size, so the original configurations can be used. As i couldn't find one, I calculated it, and made one. Update: I Changed the teeth-structure, should give a better grip. Feel free to inform about problems in size or grip etc.