Take the V-berth pads out and trace them onto giant pieces of paper you tape together. Actually, just do one as it serves in a flipped over fashion as a template for the other pad. Go to any upholstery shop and have pads made as I doubt you can sleep on the stock pads without aching hips; get 1.5 to 2 inch thick foam. Get zippered covered as you may need to wash them eventually.
They will also make you fitted sheets. Not being female (I guess) caused me shock to discover the cost of sheets; i.e., ≥ $50/set. Buy 2 decent king size flat sheets and have one "fitted" to the the foam, and another cut to a v-shaped sheet with some overlap to use as a top sheet. We had 4 made to allow for one to be in the wash while another "set" was on the cushions. They need only fit over the 2" foam you have made to sit on top of the rock-hard stock cushions. If you are under 60, you might tolerate the stock cushions.