I've seen the Rino Lining type stuff (actual product was Line X) sprayed in the bottom of small aluminum boats before and it makes a nice durable coating. The only problem is that most of that stuff comes in black and it is just about as hot as the bare aluminum. I had an aluminum boat one time that I cut plywood to fit the bottom and used a staple gun to attach astro turf type carpet to. I did not attach the plywood and you could just popout the sectionsto clean underneath. Having the wood on the bottom was much cooler and muchquiter.