i have been covering my planes with silk or ceconite type covering for over 50 years and have always just given two thick coats of buterate dope on the outside edges. then when appying the covering the coat of clear soakes through and bonds with the balsa coated balsa.. i also always use silver on the covering to protect from sun damage. i have several old models coverec with silk that are well over 35 years old and the covering is still good.