Default Cessna 172 banking to the left

Hello all,

On my computer, the default Cessna 172SP has this terrible tendency to bank to the left in level cruise flight, not only during climbs, where this tendendy is expected.

I have to fight the aircraft so it maintains course.

I have the Carenado's C152 and C172N, and of course, flying those are a whole new ball game. But my interest on the default aircraft is because this book I'm using to train fro real world flight, and it uses the default aircraft.

I have seen many people complimenting the default C172SP as a great flight model, others, like me, having problems flying this aircraft. Oddly enough, I do not have any problems with the other default aircraft.

What I'm looking for is not an entirely new flight model, but to add stability to this plane.

I have made modifications to the aircraft.cfg file, changing the roll, pitch amd yaw stability from 1.0 to 2.0, and that seemed to help a little.

However, I have read elsewhere that the real changes take place on the .air file.

I have the editor for this type of file, and if someone already had this problem and solve it, that please, help guide me to solve this problem. 

Thanks.