I began running Supercat with a 3/4" plywood floor in the Captain's bay. I replaced it with Polymax after getting hung up on a low-head dam full of wood. I've been completely happy with the water passing through, getting wet, and not being held in a hole by a bay full of water. On several recent Westwater trips with weekly regulars I have been advised to put in a solid floor which will lift me up on the crest of waves rather than them slowing my downriver momentum by being held up in bays. I can see both perspectives and find Westwater's rapids different then my usual day runs.
Perhaps I should approach Westwater differently or keep my current setup!?
At some point don't you start affecting the performance of the Cat in the stability department? I always assumed that the reason they did so well in the rapids, not flipping as easy and such, was because of their open nature.
I made diamond plate floors for my 16' cat for a recent July GC trip. I was completely happy with the performance in the rapids. FYI - I spanned the 39" between the rails with 1/8" plate; bent both long sides 1" over at 90* for strength/support and made different width floor pieces. Used 2 - 12" wide pieces for the cockpit area and was happy with how little flex there was. I also got longer bottom rails; extended the rails past the yokes on both ends and had a 6" piece of plate in the front for a step and an 8" piece of plate in the back for the groover (and as a step) These frame extensions didn't seem to affect performance and I wasn't worried about rocks due to the high flow.