I suspect everyone has their own solution to this problem. I picked up a 4" memory foam bed and replaced the stock cushion with that. You cannot however use that same memory foam for the seat as I quickly discovered.  While memory foam is nice to sleep on, it compresses too much to sit on.  I use high-density 3 inch foam for the seat, without the Contour or bolstering design (I like it flat-- more comfortable to me) and then I topped the whole thing with a piece of one of the half-inch memory foam. I sleep with my head towards the rear door, so the rear cushion takes the bulk of the weight. The cushion tends to move TOWARD the seat this way as well, and avoids a hole there. Extremely comfortable. Just be careful getting up as I whack my head about every other time!

For the top bunk, I used a 3" rollup type bed from Cabella's. I took the top cover off and cut up the foam to be the same size as the stock. I then had new covers made, well I sewed them and attach new snaps. Two pieces of 3 inch will not allow the top to close, so I removed the front pad and place it over the rear cushion above the engine when not in use. Four snaps secure it when needed+ some velcro between the cushions. I also use the same one and a half-inch piece of memory foam topper up there-- now that's a comfy bed! I use "space bags" to compress the topper when not in use. Can you tell I"m not much into roughing it when it comes to my back? My thermostatically controlled furnace completes the package in the fall--ahhhh bliss!

Troy