I am in the process of repairing a 4* 60. Much of the lite ply shattered on light ground contact.

An access hatch for the tank might be a good idea.

Facing the formers at wing front and rear with 1/64" lite ply would make them more durable. Triangle or Sq. stock would also tie all formers to the fuselage more securely.

The fuselage behind the wing breaks easily and could benefit from facing the fuselage sides a few inches back from the rear of the wing.

The fuselage in front of the tail feathers is also weak.

Bill