I welded some into my demon- wow what a difference just normal driving. A lot of squeaks were gone, it cornered flatter, launched straighter, just plain felt better. Night and day. I used 1/8" wall 3x2 steel and instead of notching the floor I notched and tapered the rear up to surround the front of the rear frame stubs.
Sorry to pile on the bandwagon even though I don't have any twisting at launch info but just do it!