How about strapping/stretching on another fabric top. Keep the flying buttress profile, covered or uncovered rear w/ a clear PVC panel. There are MR2 rear lip spoilers that where the fabric could 'bed-corner' on. Just doodling out loud.
http://i.imgur.com/1W3rX.jpg
http://i.imgur.com/Azq6c.jpg
http://i.imgur.com/UM5PS.jpg
http://i.imgur.com/cDb0g.jpg