[jdm4x43732]

I have a 1648 Alweld boat I picked up to put my Go-Devil on to do a little duck hunting and maybe chase some reds. It has ribs 12" on center and if the kids come with me I don't want them to trip walking in the boat. Any of you have advice on what thickness plywood to use on the bottom, aluminum would be better but it isn't in the budget for now. Read a few places that treated lumber will eat up the aluminum. Anyone ever had bad luck with this? I'm gonna paint what ever I put down and waterseal it.
thanks guys.