What spread are you using?
I take it this is designed to mount into a non WCD style drive? I bet you could probably flip the motors around and hang this over your wheels if you use a 24:60. Also I think your weight calculations are off. To be almost 2 lbs lighter than the DS Standard 3 CIM you'd have to weigh: ~2.8 - 2 = .8 lbs
http://puu.sh/8Zy3d/55951f0c15.png
and your probably around the same weight due the fact the internals + motor weight is about the same. Weight of 3 CIM DS Standard (Non WCD)
http://puu.sh/8ZxQA/bb0bb3d496.png
EDIT: *Are you comparing weight to the 3 CIM WCD with PTO?*