Thanks for all the posts everyone.
We ended up buying a 4" thick memory foam topper from Walmart and I used an exacto knife to cut it to the correct size and shape. I had enough left over to make one cushion for a settee and some small "throw pillows" for lounging in the cockpit.
All in all it was money well spent and I slept like a baby on Friday night. It was a bit cramped but my wife is a bed hog
I'm definitely going to put a 4" topper on my bed at home and on the big boat when we get it to..