Hi,

your problem is a misunderstanding of the physics. In a room without air, an airplane (and any other object) just falls to the ground without changing any angle, i.e. it falls as it was dropped. Center of gravity has no influence on that. What makes an aircraft fall nose first is the balance between lifting forces at the wings and the tail in combination with the center of gravity. So, what you would need is a simulation of the aerodynamic forces at wings and tail. Maybe possible. Look for aerodynamic lift formulas. COG should be at 1/3 of depth of wing. Ah, you can shift the COG by an additional mass inside the aircraft which cannot be seen from outside.

Good luck
Henning