Shug- I think stiffness is an important issue for flaps. Silkspan will help there, but shrinking dope does bother me. I recommend the .56-oz fiberglass and epoxy route. You'll get a lot of torque resistance, if you bias the weave to 45 degrees, but care is important in order to avoid a real mess! (carefully roll each piece up so that you can roll it out spanwise over a very thin - squeegied - coating of epoxy to start). If you do this and then follow up with a second coat of epoxy, after the undercoat as set to a tack, sanding later down to the weave, you will avoid the glass floating up - same with silkspan. You can dope over slightly roughened fiberglass. I have found that fiberglass takes so little epoxy to fill it that you can actually come in under the weight of dope/silkspan or epoxy and CF veil. I don't recommend dope applied over woven glass, because it may shrink and warp the flap and also because it keeps shrinking and revealing the weave pattern.