It's wet because the seal of that platform is insufficient. It will flex like it did before and let water into the bowels of the boat. If you do reinstall it...seal it and mark it but
make it permanent if you would ever have to access the tank again,
I entertained the same idea of using mine over but I see nothing but a lose lose situation. I want my tank completely coffined. You could pb it into place, of course with hatches for the access areas you need but in my opinion it's a dog design by boat mfgs. Too big a spread and will always flex = leaks.
How are you anticipating sealing that oversized floor door?
IMHO
KFC