In the latest Fly RC that I was reading yesterday there was an article on making cheap but strong wing bags from Reflectix which is insulation made from bubble wrap with silver material on both sides. You can get it a home-cheapo, here's a link:

http: //www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=100020855&l angId=-1&catalogId=10053&ci_sku=100020855&ci_src=14110944 &cm_mmc=shopping-_-google-_-D22X-_-100020855&locStoreNum=6675&marketID=29