We did cockpit cushions out of sunbrella and dryfast foam so they can stay in the cockpit all season. It makes a HUGE difference not hauling them in and out of the boat every time we get there...
We used 3 inch dryfast foam from the foamfactory and Phifertex Plus Vinyl Mesh that we got from Sailrite for new cockpit cushions for our Mac and really like them. Even it it gets rained on the water goes through so well that you can get by with a doubled up towel on them and they dry really fast. We worried if we would like the feel of the Phifertex on bare skin, but it isn't bad.
We plan on making the same type of cushions for the Endeavour and brought the current cockpit cushions home for patterns.
We also like the firmness of the dryfast and find it to be about right for us. We considered close cell, but it was too firm for us.
I would tie the cushions down most nights in the Mac as we didn't want them to blow away. The new ones will have loops on the back for a line to run through and we will go back and add the loops to the other ones.
Making the cushions for the Mac is on our site,