What If Build Ideas...for Land Speed Racing

I would contact BNI/SCTA and talk to someone regarding your cage. They have specifc requirements. You do not want to get there and be told your dafety equipment is noncompliant. I know other guys have arranged to meet their tech inspectors for pointers. Better to load up and meet before you get too far along. Remember that on the salt low aerodynamic drag and weight are your friends. Some have bolted 1" steel plate to the bottom of the frame. Talk to the tech guys. It will save you in the long run.
We do the exact same thing in drag racing. The tech guys kind of have a side hustle helping to ensure folks build per the rules. Contrary to popular belief most of them genuinely want safety not just to be a Dick. There is invariably someone in your area that will make a house call. It is a priceless investment and will save untold grief. They are typically a wealth of info and are in the hobby for same reason you are, pure passion.