Re: Rule 3.1.4 - spreader plates
Mulry's post is spot on. The square inch rule isn't set in stone. I've been emailing Nick and John about this. Our Autopower bolt in cage has 4"x3" spreader plates and I've been told they are still acceptable, but they highly recommend beefing it up.
We originally got a bolt-in cage because we were running at Altamont and with the demo-derby style racing, we figured the car may be a throwaway after a couple of races so we could transfer the cage to another car (plus it was cheaper than a custom job). But 5 races later that's obviously not the case. We've put enough work into our car that I'm not going to dispose of it unless it gets heavily wrecked.
Our cage is meant for cars with moonroof and full interior, and of course our car has neither, so the cage can actually be raised up about an inch or two closer to the roof. So I'm taking the rule change as an opportunity to make some improvements to the existing cage by raising it up on "plinths" like the original poster's photo and making some other changes. John said this style of mount is perfectly acceptable as long as you use 3/16" steel and fully box the "platform." And yes, vertical plates (either the plinth style or by just adding a vertical piece that ties the foot plate to the side of the door sill or any other vertical part of the floor pan) counts toward the square inch rule.
