I find it strange to begin with that someone could blow out their floor, unless it is due to overloading the boat with gear on the floor itself. I thought the idea with gear rafts was to have a frame and the load goes on the frame which bears on the big tubes, not the floor. If the gear is bearing on the tubes, the only thing on the floor should be occasionally feet or maybe beer cans.
On my duckie, I just put a cork in the PRV that's sawn off just to stick up enough to get it out. I carry a spare in my drybag in case it pops out, which it hasn't done yet. They were about a dollar.
My duckie has been submerged when wrapped around rocks several times when fully pumped up which probably at least doubled the pressure in the tubes and also floor and everything came out of it just fine. The cork didn't even pop out and it's not in there very tight at all. Just enough to keep it from falling out by itself. Before the cork, every time I went over a drop my body weight would cause the valve to squirt out some air until the point where I had to top it off. There's no leak, just a poor design.
It's obvious the PRV copied a car radiator cap principle. However a car engine does not have bursts of overheating and rises in pressure. When the pressure rises, something is wrong and you want it to leak. But with inflatable watercraft, intermittent increases in pressure are normal and if a PRV is rated at x PSI, the point it ' leaks ' some air out is probably only .1 PSI over that since the floor is usually initially inflated up to where the PRV leaks. Hence the air squirting out on drops, rocks, etc. Is that going to pop the floor if no PRV ? Not unless there is a ton of weight on it.
So, what's better ? A calibrated PRV + a Calibrated cork. Just a cork is no good, because if it pops, you lose all the air. Nobody wants that. Just lose enough air to stay just below floor design pressure danger level yet ride out short intermittant increases that are absorbed by the crafts flexible materials.
Maybe like the flappy thing that goes on some weatherproof cigarette lighter plugs.They have a kind of round rib on the cap and a matching groove in the socket to keep it in place. And a very short tether going to a ring around the underlying surface so as to not lose it if it pops. Have that calibrated just below the maximum design and tested pressure of the floor then have the conventional PRV part under it calibrated to the pressure you like your floor at.