I sent Toby Silhavy the designer of the PH3D profile model an e-mail outlining what was happening with my model, and he replied suggesting a couple things to checked.

It turned out that the elevators/ailerons were not at 0 degrees when at neutral. The ailerons had a couple degrees of up, which also explained why the model always needed a very long takeoff run before getting airborne.

Karol