N1EDM, I've been following this thread since it's, one, an interesting problem, and two, because it's purpose is so puzzling to me.

But anyway, I have a lot of experience with fibrous coverings including Silkspan, Polyspan, Litespan, Airspan, Jap Esaki tissue, Koverall and silk, and others I can't remember.

In my own experience, nothing provides as taut a surface as real silk filled with several coats of nitrate dope. The drawback is that it takes a long time before it fully cures and finishes shrinking, as in weeks or even months.

Other than filling the open areas with solid material - which I know you don't want to do - I'm not aware of any fibrous material (such as silkspan) that will provide as tight and rigid a surface as Jap silk and nitrate when properly applied, sealed and shrunk.

I have painted 30-minute epoxy over silk that is covering open areas for the purpose of fuel proofing and almost 14 years later it still hasn't cracked. I can't imagine why the same would not hold true had I included a layer of glass cloth in the process. Applying epoxy paint over this (Klass Kote, for example) wouldn't change anything as far as I can see.

Here are a couple of pics. The pylon (wing mount) is Japanese Esaki silk, the fuse is Esaki tissue. Both are coated with epoxy. This was done in 1992.