Hi John
Nice to see it's coming along, and that you took the necessary time to ensure that it's legal.
I have always covered the entire airplane in glass cloth and epoxy resin. Although it's not absolutely necessary, it does prevent a fair bit of Hanger Rash, adds a bit of strength and makes it easier to fill the grain in the wood. I always figured, if I have to fill the grain anyway, might as well add a bit of strength and resilience as well.
I've never used Polyester resin without glass cloth other than some testing scenarios. Without Glass cloth, the resin is very brittle and chips away easily when impacted. Polyester resin can also cause surfaces to warp during curing, more so than epoxy resin in this application.
If your wood is very hard "C" grain, you might get away with resin only, but still watch for warping.
Looking forward to seeing it painted.
Les