How about a pattern in the minicell?
Stripes of different roughness? Rough sand stripes, or pull the final sand paper in different directions so the light reflects differently from directions?
Might want to talk to a company that refurbishes furniture, or that supplies foam and fabric to refinishers. (In Los Angeles I would go to Diamond Foam and Fabric), these guys would have a deep body of knowledge.

Another great material I've been working with (but would be difficult to follow the concave/convex curves of a seat) is high strength window screen. It's black mesh, designed to keep pets from shredding it or kids kicking through. My old incontinent dog needed a pee proof bed. I stretched some across a rounded square of PVC electrical conduit (the 90 degree corners are long curves). It's like a trampoline. (underneath is a 28" diameter round water heater pan) I can hose it off, slap the water off it and dry it on the porch in under an hour. Cost less than $20, and I've still got half the roll.

6-8 months ago I used it to replace the mesh seat on my office chair-- it hasn't stretched or sagged since. My stretching technique and attaching though needs some work. The dog bed is held with strips of PVC screwed every 6-8 inches. It won't run or tear.

If I could figure out how to stretch it into a tractor seat shape it would definitely be my choice for a kayak seat. It's similar to the material used on Aeron Chairs. I like the way it gives just a little under my thighs, and it's just a little less friction than minicell foam-but not slippery. Very comfortable.
I wouldn't be surprised to see it used on airline seats.

Now I'm thinking, maybe, if I had a frame underneath, so there'd be an attachment point in the center....