Hi guys,
I used Minwax Polyurethane (water based) and fibreglass over balsa to cover my Pica 1/5th scale P51. It goes on like a dream and fills nicely with 2 or 3 more coats. The beauty of this product is that it is 80% water which evaporates off and there is no smell.
IMHO I think that it is a great product when used as above. I do not know how it will work over open webs.

All the best

Mike