troyp,
The biggest problem flying inverted with most trainers is the dihedral.

Trainers have a lot of dihedral in order to make the plane more stable in flight. The problem is, once inverted that dihedral becomes anhedral, which means the plane will constantly try to roll out of inverted to upright.

Add a flat bottom wing, and incidences set to maximize stable, upright flight, and inverted (or most aerobatics) become a real problem.

The good thing? If you become fairly proficient at inverted flight, and other aerobatics with your trainer, once you get that second plane you'll be thrilled with how much easier it is!
Dennis-