I had a local fabric
shop put together a custom foam mattress for me, very cheap
. They laminated a piece of low density foam on top of a piece of medium density foam. Cut to specifications. This was put inside the existing canvas
I had for the vee berth.
It was terrific. We spent some time with me trying out different combinations on the floor. I ended up with a 6 inch mattress.
To that, I added a 3 inch topper of memory foam, bought off the internet
for $100. Cut it to size.
WOW...heaven on earth. I have never been in a bed
I liked more. Never slept better. And all very inexpensive.