Here are the simple steps I took to install my Redfish Kayak seat in Black and Tan.
I've struggled trying to make comfortable kayak seats for years and have tried minicell foam, inflatable cushions, gel pads, and off-the-shelf ready-made seats in combination with all kinds of backbands. Finally I had to give the Redfish Kayak Seat a try since everyone I've met who has sat in it says it is the most comfortable kayak seat they've ever tried. Joe Greenley will carve a seat custom fit to your dimensions and cockpit. He keeps templates for various kayak models (both wooden and fiberglass production boats) on hand. A Cadillac among kayak seats, the Redfish custom seat comes with integral hip pads and back pad and runs about $145. The seat I got from Redfish was just a "pre-sculpted seat blank" that Joe sells for $48.
The original seat had a wooden backband that I really didn't find comfortable at all. It also tended to twist around on itself whenever I got into and out of the kayak.
First I marked out where the new seat would go by locating the deepest part of the new seat where the black circles were on the old seat (the location of where the "sit bones" go). Then I made a pattern of the cross section of the kayak using two spare pieces of foam core. I drew on the foam core by tracing along the inside of the kayak with a Sharpie held an inch from the kayak panels with a block of wood. By cutting out and taping the two pieces together I made a pattern that matched the inside cross section of the kayak at the from edge of the seat. If the cross section of the kayak at the back edge of the seat is significantly different than the front end, you should repeat the process for the back edge.
Then I traced the pattern onto the seat blank. I used a handsaw to rough out the shape, then shaped the seat further with a Stanley Surform tool. Sandpaper works well for finishing minicell foam and gives it a smooth surface with a texture like suede.
The seat popped right into the cockpit with a little twisting. I secured it to the floor with Velcro strips stuck on with spray adhesive, so I could remove or reposition the seat easily for future adjustments and repairs. In combination with a couple minicell knee braces, the seat turned out the be the most comfortable kayak seat I have ever used! I can paddle all day in it, and it is deep enough and provides enough sacral support that I don't even need a backband.