You won't want to go the spray-on bed liner route. I know some drift boat guys that tried that when spray-on bed liners first came out and I've heard or a couple of jet boat guys that tried it as well and all regretted it immediately. The rough bed liner surface increases surface drag and sticks to every rock like Velcro. If you are wanting to do a coating, you need to look at the ones they make for airboats, like GatorGlide or similar. You can also add a UHMW bottom, which work great but will cost a fair bit and do add a bit of weight to the boat. Plus, UHMW is screwed into the hull, so you would have decide if you want something screwed into your boat on a large scale. You can also look at getting the bottom double-layered with aluminum. My boat mechanic used to weld double bottoms on jet boats when people wanted them, which made the boats heavier, but protected them well and fixed boats that had really worn out bottoms. If it were me, though, I would just run it like it is and if you put a hole in her, get it welded up. The added weight created by adding to the boat's bottom may be more detrimental than just leaving her as is.