I have been continuing to build some test models. Got rid of the motor tube and tested a fuselage that could withstand the torque of the rubber motor upto about 100 turns or so.
Following previous advice, I have started experimenting with a non scale stick plane with originally a 40 cm span and weighing oh maybe 20 grams or so due to styrofoam wings. Replaced the styrofoam wings with bamboo and paper and the model flies surprisingly well, although impact resistance and water resistance is very low. (I'll say!) Also deformation is also a big problem.
All this will be solved with a new design taking inspiration from this designer in this post:
already a test wing has been built and is quite strong but weighs 7g per side for a 30 cm span wing. Will post pictures of it all. What a journey.