I've been sleeping on air mattresses since 1994. I find them to be very comfortable, but there is the dampness problem. You need an absorbent layer between you an the air mattress.
As for modifying an air mattress to fit a vee berth, I suspect folding under would be the simplest way. Back in the day when they were made of rubberized cloth, i always figured on cutting one and restitching with a sealant
. Today's versions are cheap
vinyl, and I never get much more than 3 months out of one before one of the internal baffles lets go and you end up with a huge bulge in the mattress. If its off to one side you can sleep on the other but if one has let go, the next one will let go soon. It makes a god awful bang too. I've been tossed against the wall when two of them let go one right after the other on the edge of the mattress. I weigh over 300 lbs and have a bad back which is why I use them. But it tossed me aside like a bag of laundry
. I've never had one pop, but the baggles going is standard for them. Some also hold air better, and some leak no matter what you do. I get mine from Walmart and I can tell you, the quality is the pits compared to their first ones. The high cost of low prices means your quality is less with each iteration because they tell the supplier to cut by X% or lose the contract
. My first one came with a double action pump that I'm still using 16 years later. The new ones are piddly little single
action jobs I toss out immediately.
I don't know if they still make rubber and cloth ones anywhere in the world but I'd try to find one if they do. I still have two for the early 70s that work perfectly but they smell musty so I only use them for camping where I can wash them in the lake every day.