I'm building a Tundergazer type fuselage (not a take apart) and I don't remember what the former by the flap horn is made of 1/8" balsa or 1/8" lite ply. F1,2,3 are ply because they hold the motor and battery but what about the one right behind the wing?

  I can see no good reason for that to be plywood unless you are making it a "from the bottom" take-apart and need it to hold the screws. My former in that position is built up from 1/16 x 3/8 balsa strip.

    Brett