Jim,
Glad to see you are refinishing the teosawki, I have a couple of original built by Clayton, The latest one I obtained from Allen brickhaus family after he passed , the best I can tell , it was next to the last one built , I think Gene Martine has the last one
Mine appear to be covered in some type of light tan /white paper , different from silkspan, could be some type of tissue paper , I can sand it off , it blends easy , so it is applied with some type of glue that is clear and very sandable . Who knows what he used , probably some hi tech russian space garbage bag .
I am in the process of covering and repairing mine that I have flown for over 10 years, I too wanted to retain all of the Clayton look, including the wood thrust shims , petty blue wing tips , trick wheel retainers ( lock washers in his groves )and cotter pin pushrod guide .