Joe, I had a profile carrier airplane that was covered with Polyspan and nitrate, then finished with Klasskote. After a while, there was some fine cracking around some of the edges of some of the open bays. Knowing the quality of your work, you would probably find it unacceptable. I have wondered if any of the automotive flex additives would work in Klasskote, but have not tried it.
Bill Bischoff