I'm not too sure on the idea of working on speed sensitivity and CG before thrust line in this situation. Dbaque did a good explanation of how to tell the difference between a thrust line problem and an incidence or CG problem. It's pretty easy to tell once you've done it a time or two, so I don't see the point of working on CG or incidence if it's obvious there is a problem with the thrust line.
To add a bit to the discussion, getting the thrust line set right is really all about making the engine pull in exactly the direction that centers the plane's drag at its CG. So high wing planes need some down thrust and low wing planes usually need some up thrust depending on how much dihedral they have. There is more to it than that, but the basic goal is to set up the thrust line so that just the addition of power does not create any pitch or yaw effect. Speed changes often cause pitch effects with a properly set thrust line, but that's a completely different aerodynamic problem to solve. When setting up an aerobatic plane, the pilot often has to make some compromises. If you tune the thrust line for best flight at cruising speed, it may be off for vertical maneuvers and in a nose up stall with some power on. So your loops may track perfectly upright and inverted, but your hammerheads want to fall off to one side consistently. Many many thousands of hours have been spent by designers figuring out how to reduce or eliminate those kinds of conundrums, but they will always exist somewhat.