hello, I just waned to share with everyone the benefits of working with fiberglass resin and fleece. I know that we all love our coroplast and cardboard..hehe. but... if anyone is looking to build some more durable body panels I recommend looking into fleece....yes fleece, like a blanket. I've included a picture of a front bumper I had made a while ago for a cavalier that I no longer own. basically you can stretch the fleece material over top of whatever body part you are looking to create. then paint it with fiberglass resin. if you look up 'fleece sub box' on youtube, you will get the idea. anyhow. this bumper was actually quite strong and light. and you can achieve some great curves with the material. sorry I don't have any data on the bumper as far as mpg goes.