[JesseK]

Foot for foot, 80/20 aluminum isn't that much heavier than 1x1x0.0625-wall extrusion. The biggest weight difference is in the fasteners -- to stiffen the 80/20 frame, make sure you allocate enough of your weight budget for plenty of bolts. This year our lift overran it's original weight calculation by ~15% due to extra nuts/bolts that were added at the base.

We used 80/20 for our lift in 2008 and noticed severe torsional forces when the lift was high and everything was under stress. That said, I'll echo MOE's comments that the frame needs to be stiffened at the end of every match. Another option is to sandblast/clean off the outer coating, and weld it. Usually a local machine shop is willing to donate an hour for this if you time it correctly and plan in advance. Welding would significantly improve the stiffness of the frame. Even better, you could take a 80/20 'jig' in, bolt the frame to the jig, then the welders would have plenty of room to weld the frame joints together without worrying about having to lay out your frame, or warping as the frame cools.