Read where folks are covering foamies with lightweight silk and water based polyurethane.
Silk is available in several weights from Dharma Trading Co, mail order. I have some of their lightest silk and have used it to cover a wing the 'old' way, with nitrate dope. Pretty nice stuff and not particularly pricey. Polyurethane is available in my area at both Lowes and Home Depot in quart and gallon cansunder the Varathane label. Supposedly Minwax also has some but haven't seen any.
Haven't tried it yet but will when the occasion arises. You'll see references in forums as WBPU.
I have used aerospan (also called polyspan and dress interfacing) with epoxy with good results. Its best for flat or single curve surfaces as it shrinks with heat but does not stretch. Being a non-woven fabric it does not want to tear and the epoxy or dope permanently adheres it to the balsa.
Hope this helps. If you find a solution that works for you, please post.