As everyone else has said this is a great first start into the world of custom drivetrains. Just two bits of advice. As everyone else said you could go down to a much smaller sprocket size for your outside chain runs. The other is that you need a little more reduction. Judging based on the picture your current speed would be 40 and 17 feet/second. In real life the robot would barely move. However vex does sell a third stage reduction kit for the 2 cim ball shifter. This moves it down to a more reasonable 13 and 6 feet/second at your current setup. IMHO a fairly good speed range for FRC. Just my thoughts, Hope it helps. And for future reference and doing these calcs yourself I would recommend downloading this.
http://www.chiefdelphi.com/media/papers/2755
It's the starting point for a lot of FRC drive trains and mechanisms.