I'm all for 80/20 in the right situation. The best use of it on a drive system I've seen came from my alma mater of 1293 in 2007. Consider:
http://flickr.com/photos/billfred/1337894883/
The two bolts centered vertically with the 1293 are 1/4"-20 bolts holding each drive pod to the center rails, which appear in
this photo to be 1515. Heavy, yes, but it's a pretty short length. The 1515 goes straight through to the outer plate on both pods, tying it all together (and providing pretty awesome nice mounting options for a mechanism to boot).
They haven't had any issues with that aspect of the robot to my knowledge, but I also changed teams right before that season. Someone who was active with D5 that year may be able to tell you more.