Have you thought about buying some thin plastic sheets to cut up and glue/melt into the shape you need. This way when/if you wreck it would be cheaper to replace. You could also use spare pieces inside, if you leave it hollow and open ended, to give you a little bit of down force. I'm not really sure how well it would work, but there's a slight chance. Unless you play in mud. I'm thinking of adding a angled piece of body inside my rollcage to push more air onto my engine since the body sits so high now.