Hi Abufletcher, to answer your questions, my opinions only -

1. Changing the incidence on the stab is just like elevator movement or elevator trim. On full size aircraft it's used to adjust the trim of the plane so the pilot isn't pulling up or pushing down on the stick to allow for changing speed/load/balance situations. If you raise the front of the stab it's like lowering the rear of the stab, like lowering the elevator, tail comes up - plane goes down.

2. Wing incidence is very critical, usually adjusted at first by trial & error or a guess following experience with similar models. Just build as per plan would be my advice, go with the forward limit for the centre of gravity for the first flights.

3. Yes. And with the engine thrust line. If the wing, the tail and the engine are all in one line (like an Extra 300 and most aerobatic models) and the wing section symetrical or almost symetrical there's a good chance all three will be set at zero degrees - the model is like an arrow & will fly fairly straight regardless of speed or whether its upside down or not. When you start raising or lowering engines, wings and tails things go out of whack so the angles are then changed to make aircraft fly correctly. Raising the wing incidence is like lowering the tail incidence, the plane will tend to loop. If the wing incidence is raised more than a little the tail incidence must be raised as well to keep the plane flying straight.

Hope this helps - John.