I realise best way to conventionally do it is to CA / Glue. I am concerned there isint enough bearing area of wood-to-wood contact for either glue to work. A friend who did up his version with 1/8" balsa sheeting in all open bays to strengthen, now suggests to use CF stringers laminated between the original (very thin) ply and 1/16" balsa formers. My concern is this will add weight. In his case, he is flying with a 120ax which would be more powerful than the dle20 I intend to use, so I want to keep the weight down. Frankly I am thinking to use 1/8" balsa sheeting with lightening holes in all bays and 1/4" tristock at all intersections

Ameyam