Ok it's a done deal. After much testing at the foam shop I decided to go with extra-firm, 10 year density foam for the whole bottom cushion. It feels 100% better on my rear-end though it's brought up some new issues.
1) The table will need to be raised by about an inch or so and the outside corners cut-back to ease entry/exit and use of the table while seated.
2) The back cushion sits on top of the bottom cushion and is captured at the top of the back cushion by an upholstered board. With the new bottom cushion installed the back cushion is almost non-existent in terms of support and that top board impacts my back solidly. Guess I'll try stuffing some extra foam in that top cushion to see it that helps.
