Team971 uses .090" 5052 H32 in their designs. Last year we switched from .125" aluminum because we can save up to 27% in weight of our chassis. Also the laser processing time is much faster using a thinner gauge material. 95% of the robot parts are designed from one thickness. The team builds a competition and practice robot so we nest the parts on a sheet to utilize as much material as possible and to decrease our process time on the laser to cut down on costs. Our fab sponsor is happy about that.
It's been an evolution since 2006 and the .250 thk chassis but the team's CAD group is getting real good on how they design the folds, joggles, rivet holes and lighting patterns to maximize strength and chassis stiffness. They are confident so we are thinking of going with .060 5052 this year.
Figuring out if the parts are stiff enough and light comes from experience and iteration of the chassis design. I always suggest to go for lightweight design and make extras then at the end of a competition season do a review and save the info in your robot toolbox for next time.