Good points Bax,
I would add something concerning upthrust.

As previously said, up and down thrust is used to avoid any pitch changes with throttle changes. They are dependent on airframe shape and drag distribution it creates around vertical CG: in trainer planes, wings are over the CG (see it from the side), so as speed increase there is a pitch moment towards the wing, since it is generating more lift but also more drag. In amphibian planes both high mounted engine and high drag made by fat "gears" call for the need of upthrust.

In my depron aerobatic plane, similar to a katana, I had to add some upthrust. When I watched the plane from the side, I was surprised how much upthrust to have a neutral behaviour. Later I discovered that it seemed that upthrust was in place, instead the motor was aligned with stab (and wing): it was the fuselage that gave the wrong impression.

This is to say: add down or up thrust if needed to have a neutral airplane with respect to throttle changes. And remember to watch engine incidence with respect to stab and not with respect to fuselage nose...