Years a go I built a Super Emeraude for the seat I cut a form out of Styrofoam with a hot wire like the model airplane wings. Then glued 1/8" ply to the bottom and put 1" foam over the top and appolstered with fabric. I drilled 4 holes in the plywood airplane seat bottom and the seat back they except wire snaps so the Styrofoam ,foam and applstred cousions can be removed in just a minute and you could cut different shapes for different people. Joe