Well,
I have settled on reticulated foam at 2 inched high density. One interesting thing I learned about closed cell foam is that while once upon a time manufacturers kept it in storage for several years to let it "shrink" to it's final size, that is less the case these days. My own experience with closed cell foam was a set of cushions that shrank along their length several inches in the two years I had them. That and the ever rising cost of the petroleum based product has made it less used than it once was. The big problem with reticulated foam is that UV destroys the stuff. Unless you wrap it, it doesn't do so well with the mesh fabrics. We are leaning toward Sunbrella again...... It is really nice to sit on and if you keep at it you can keep it clean.
We'll see. Thanks for the responses!
Bruce