I agree that the characteristics you observe are caused by the positive cambered tail. It is lifting too much (or not providing enough down-force). That's why so much up-trim.

Raising the thrust angle has the effect of moving the CG backward under power. This frees the tail up to lift even more. Sounds like you need down-thrust, not up, but you need a better tail airfoil even more if you want to do aerobatics.

Incidentally, just because the tail has a positive camber, does not guarantee that the tail lifts. If your CG is at 25-30% MAC, it almost certainly is not lifting, but rather pushing down as is conventional, but with the disadvantage of having a positive camber.