IMHO If I were doing this project, I would not worry to much about the covering material as much as the paint,, Dope from my experience is what actually gets brittle, not the covering. because of the inherant nature of Laquer materials, they dry continually forever and ever,,. Were I to do this project I would minimize the amounts of dope used and instead use catalyzed products, (car paints) Since this will be on display and not flown, the major concern of those unfamiliar with auto catalyzed  products , that being weight build up, is really a non issue,and the Urethanes will last indefinetly when not being exposed.
Just my two cents worth.