A Professional Point of View, I think
Paul, The first thing I must say is that I am not using this forum as to advertise, for free, on Phil's nickel. Secondly, you must have an appreciation that the only type of foam that exists that would suit your "offshore" sailing purposes is the PVC/Closed Cell type. We likely all understand the properties -- one can step on it under way safely, and it does not absorb water. It's otherwise perfect, except it sometimes shrinks. This foam is made in a flat format, not exceeding 2" in thickness, rather hard, and very dense.The two company's you contacted cut flat pieces of this type of foam, dip them in vinyl, ship them to you, and in little time, you have the same shape, a little higher, and a little softer."Profile" cutting of foam is a reality -- we do that all the time for interior cushions -- but, I much doubt that even if one laminated several pieces of flat PVC together, you could not cut through the length of your seats with a profile saw, especially in PVC foam.Where you willing to give up the "under way footing" advantage of PVC foam, you could use a product generally referred to as "Dry-Fast" foam. It is the exact opposite of PVC -- it lets water run right through it, but It's considerably softer. This type of foam can be profile cut, but would require a cut-and-sew covering. Also, you'd need to consider the effect of dealing with 3" of thickness or more, and how that effected your total seating above the floor. Honest, you don't want to have your feet dangling.And in closing, and to prove my very first point, Paul, I don't have patterns or templates for your cockpit cushions.Shoud you care for yet another, perhaps differring opinion, the folling link provided.