Ensolite, as mentioned, might be more comfortable.
But best to try different material or thicknesses to see for yourself. Going thicker might not help, so better try first.
You might find that thicker closed cell foam is firmer than thinner. I know that sounds odd, but I'm pretty sure I read that to be the case. It would be like when you press into thin foam, the foam gets displaced laterally (air bubbles/cells don't compress but so much). Thicker foam will hold its shape better so won't allow so much lateral displacement. Thus are firmer.
Anyway, that was the only explanation I could come up with.
So try before you buy! I have some (C-Cushions) that are 1/2 inch thick.
But best to try different material or thicknesses to see for yourself. Going thicker might not help, so better try first.
You might find that thicker closed cell foam is firmer than thinner. I know that sounds odd, but I'm pretty sure I read that to be the case. It would be like when you press into thin foam, the foam gets displaced laterally (air bubbles/cells don't compress but so much). Thicker foam will hold its shape better so won't allow so much lateral displacement. Thus are firmer.
Anyway, that was the only explanation I could come up with.
So try before you buy! I have some (C-Cushions) that are 1/2 inch thick.