We use Butterfly on Team Neutrino and we really like it. As far as the point about pushing it down while being right above, I never really thought about the force required to lift the robot 30 pounds per pneumatic cylinder/piston, but I just really like the awesome low-rider effect (and the piston sound with it)
Also, having the axle through the omni is REALLY nice in that you just have to remove 1 bolt if you need to change modules out
Also as far as the side impact forces, wouldn't the twisting/bending be directed to the side plates which would be held in the frame and restricted on how far they could flex? We used steel for our side plates which seemed to work well.
Check out our
CAD/Info Page here and how we integrated them
here (and a video of the pistons down
here).
Feel free to message me with any questions