The drop stitch floor is a great option if you are not going to get casting decks. It is not as good as casting decks, but it is better than a standard floor.
I have a call into RMR to check on their max PSI recommendation for the drop stitch floors, but I am guessing it is around 8 or so. Most of the Leafield Pressure Relief Valves in a standard I beam floor are around 2.5 PSI. The drop stitch floors do not use a PRV. Anything over 5 PSI in a drop stitch raft floor will feel pretty tight. Most of the SUP these days are getting over 12 PSI.
RMR's are easier than some to retrofit drop stitch floors since there floors are laced, but if you are buying new, you are much better off finding one that has it factory installed.
It looks like we are about to be sold out of all of our RMR's except for the 10.5' and the inflatable kayak. If we still have stock after today, I will post on here. If anyone has any questions, please feel free to give me a call.