Take a look at the Andy Mark
2013 KOP drive train.
In the past we've built a tensioned belt setup and then last year we used the Andy Mark Setup. It is a excellent drive setup. Easy to assemble and maintain and we had no belt ratcheting whatsoever despite playing mostly defense. We were geared to 10'/sec , 6 wheel dropped with 4 CIMs. 6" kit wheels
The width of the belts, the size of the pulleys and the dead axle make assembly easy.
I was surprised to see so many 2013 kit bots in the Curie Finals. The Kit bot on Steroids is a excellent drive train.