I agree with DocYates. The resulting monoque glass envelope is relatively much stronger than the balsa substrate, but needs to bind to the balsa to maintain its shape for strength. Incidentally, the West system is a laminating epoxy & significantly lower viscosity to begin with, so with the 60:40 alcohol dilution, is relatively easy to avoid excess epoxy.

Further to my post earlier, the West system will still heat up while in the paper cup (sandae size?), so needs to be poured to the middle of the glass surface & avoid exothermal heat build-up. Then it does not begin to set until the alcohol has flashed off. After allowing a day or 2 to fully set, I sand it down lightly with new 220-grit paper on long block, just enough to remove the surface bumps without cutting into the glass. One can feel a much smoother surface after a few passes with the sanding block. For filling the web, I follow this with a layer of epoxy mixed 50:50 by volume with micro-balloon & appropriately thinned with alcohol, since strength here is no longer the objective. Another light sanding & its ready for primer. Don't forget the blue gloves & dust mask when sanding. These are nasty stuff to come in contact with.[]

Phil