If you camp in the cold I wouldn't reccomend permanently installed memory foam - it will be as hard as a board in the cold. You will eventually warm up a soft spot with body heat, but if you move around you hit the hard bits again.
I'm thinking about cutting mine down the middle and installing 2" memory foam on top of factory foam .... then have an upholstery shop sew in some black vinyl to make up the height difference. This will allow me to install a short 16" high "wall" down the middle (stored under mattress when not in use), front to rear. I'm weird about anyone other than a woman sleeping so close to me.
Anyone sleep front to rear in their side dinette Hawk? I haven't done it yet.