: Brian: It sounds like you have built your own seat before. What kind of
: volume of mini cell did you require?

That really depends on what you're trying to build.

I prefer minimalist seating in my boats, similar to the stock seats in Betsie Bay kayaks. In most cases, the seat bottom consists of two pieces. A 9" triangle of foam, two inches thick tapered to a sharp edge on two sides creates a center ridge and some elevation at the front of the seat. A foam pad ~12" x 18" (depending on the width of the hull) and whatever thickness is desired is glued on top of that. Shaped foam blocks glued to the sides of the hull serve as hip pads. I either use a backband or pad the rear bulkhead, depending on the design of the boat. The whole thing can be done with a 24" square of 1" foam. If you want a lot of thigh support and elevation at the front of the seat, it will require more material. If you want to duplicate Joe's seats, it will require still more.