11 ga. does work fine, proper construction and gusseting is much more important then mass and bulk.... My last Maverick built with 11 ga. did 5 summers on the track then another 3 years on the street before I sold it. It's still alive and doing very well!

Also, I ran my frame ties half above and half below the floor with lots of weld on both sides. The stock floor is a very strong structure, designed very well with lots of bends and beads to increase it's strength. The most important part is to NOT cut everything apart at once on the car. I would suggest having the frame ties, main cage hoop, and door bars installed first. Then, brace everything thoroughly in the back half of the car laterally and longitudinally BEFORE you cut out any floor or structure to make room for the new!!!!