SIG Koverall is 1.25 ounces per square yard. That is lighter than Ceconite Uncertified at 1.87 ounces.

Pure Japanese silk is way less than both mentioned above.

What about applying .72 ounce FG cloth with dope instead of resin?

That would seem to be the lightest way to go other than silk.

I see no reason why glass cloth and dope will not work. It can not be shrunk but that is not an issue
on fully sheeted surfaces.