I just covered a small free flight wing (291/2") with Polyspan and am really impressed! It's light, strong, adds strength to the airframe, and doesn't cost an unreasonable amount. Try it, you'll like it. The only negative (for those not familiar with the smell of nitrate or butyrate dope, or whose wife is not familiar with said smells!!) is the smell of dope-paint dope, that is...