As long as you design your fram right with welded members, you won't have any issues. The materials we use is 1/8th inch wall 1x1 box extrusion. It's never let us down.

The only time we broke it was when the bot tipped over and got rammed 8 timed by a tank tread bot. But that was a whole different issue.

So design it smart, and you'll never go back.