I have a bench seat that I use in my V. I don't fasten it down, instead I use a bungy cord to keep it from moving around. I wrapped the legs in vinyl so there wouldn't be metal to glass. I really didn't want to put holes in the back deck. My brother in law was at one time looking at getting a V21. He looked at a few and they all had soft spots in the floor, either where the round inspection hatches weren't sealed well or in at least one case where the rear bench seat was fastened to the floor. I was lucky that the previous owner of my boat replaced the round hatches in the floor and instead of using screws he epoxied them into place making them impenatrable to water. I hope they never need replacing...
Bottom line just make sure any in-deck fasteners or hatches are sealed well because it doesn't take long for a deck to rot.