Our team did a similar design, taking a FP blue gear; then putting it in a toughbox chassis. We bolted two 9013 motors to it and attached it to our prototype shooter. It sounded like a bloody circular saw and ran nearly as fast as one, here's the results:
http://www.flickr.com/photos/wileyb-...eam?likes_hd=1
As you can see, not quite the results of bolting a CIM to the shooter:
http://www.flickr.com/photos/wileyb-...n/photostream/
Oh well, time to make our own ratios/gearbox!
P.S one of the students destroyed it by running the motors reverse when it was at full speed! Snapped a 9013 shaft and ruined the plastic gear, oops!