Here's my seat mold. I originally made one from forming a shape in sand, and filling it with plaster of paris. When my brother got his Valley Pintail. I liked the seat and made a mold of that. I covered it with seran wrap and filled it with plaster to make the basic mold. You'll notice that I have a iip on the front so that suspends the seat on an angle which is comfortable for me. My mold is also deeper than my seat actually is. I just trim the seat to the depth I want once it comes off the mold.

I use seran wrap for my release when I do a glass one. I tried mold release and damaged the seat and that's what the purple is - body filler to fair it out (again). my mold is plaster coated with 4 oz. glass and the weave filled. Real mold release will only work if the mold is mirror polished and absolutely perfectly smooth with not even a pin hole imperfection. Otherwise it may not release - take my word for it. Take your glass seat off the mold the next day because epoxy shrinks as it gets harder.

On my boats I have hip braces running from the deck to the floor and I use a bolt and finish washer/lock nut fastened into that to hold the seat much like commercial boats.