Paul
Even established companies learn during the first airframes produced where to add or subtract cloth. If you have ever seen the skins on a ‘re-kitted’ CARF Jet you would see how light a cloth is possible to layer to make a skin. Using a light cloth on the outside, slightly heavier cloth on that, then foam and another thin skin vacuumed gives a great surface finish with minimal resin and really stable skin.
Your wood structure can be reduced, carbon tape, thin ply or foam spar and carbon tape making an I beam is so strong. My father and I used to compete making balsa bridges that weighed the least and would support the greatest weight...was amazing what we got to with a 3 oz bridge spanning 18”
The L-39 gains from Eppler 205 section from gliders and the Tip tanks that stop spillage over the tips. I have flown a Jet at more than 135oz loading, most did not expect it to fly but it did! Don’t think the L-39 is actually that high...but decided not to ever calculate it. It’s one of the early AW kits with balsa instead of foam in the skins...you could beat someone to death with the wing panels and not dent them!!.
It was painted by an Automotive friend and the paint is quite thick 😉
Your fuselage will develop quite a bit of lift, so that helps. You will know after the first turn whether you are good or not 🙂
Your moulds are most of the work and they will survive flight testing 😉 Keep up the great work, everyone I speak to admires what you are doing, you make the rest of us ARF assemblers look bad!
Dave