The longitudinal centerline of what:
The fuselage geometric center?
The fuselage mass center?
The thrust line?
The main lifting wing(s) aerodynamic center?
The center of drag?
Yes to all the above?

A bi-plane seems like it would do good and look normal at the same time. However, my Ultimate has proverse roll and up-pitch with rudder. It seems like the aircraft mass centerline is the important one. I'm just guessing though.

I also heard that things like dihedral can increase or decrease coupling. I once saw a model Citabria with anhedral (drooping wings). It was intended to decrease yaw coupling with ailerons.