I hear the woes about the battery trays, I've been scouring U-Pull-Its for years looking for one that's better than mine, but finally decided mine's not in that bad of condition considering.
I pulled mine one nice Saturday this summer, cleaned the heck out of it, used the marine clean and the metal ready and took a wire brush to it so the paint would stick, then painted on the Por 15. I now have a glossy black battery tray with significantly less holes, that's much more solid. And of course, while it was out I took care of my gaping hole underneath as well. I'm happy enough with the way it worked out.