As you're finding out there's a lot more to trimming a first class aerobatic model where the flight maneuvers will be judged for style and accuracy. For example your "increase the wing incidence" rul for correcting the vertical pulling likely relates to the prop thrust as much as it does anything else. But just adding up or downthrust wouldn't do the same thing because you won't get the same vertical displacement of the thrust line with altering just the downthrust that you will with a change in the wing incidence. I sure don't pretend to know the ins and outs of precision pattern model trimming but I know enough to realize that when you alter the wing incidence you alter a lot of other things that at first do not seem related.

Another big trimming issue for pattern models used to be the vertical position of the horizontal stabilizer. Back before mixing was widely available in the Tx's pattern designers thought nothing of cutting into a model to shift the stabilizer mounting position up or down as little as a quarter inch to change how their models performed in knife edge flight. I don't even remember if it was to cure a pull to the top or belly or to cure a roll couple from the rudder. In one case a designer was up against the clock with little time before packing up to go to a major contest. Instead of the lengthy total remounting process he cut and added some anhedral to the stabilizer and made up a Y end for the pushrod to the elevators. That did the trick apparently since he won the major contest and for a short while anhedral stabilizers were all the rage with somewhere around a half dozen major players producing designs with anhedral stabilizers in the wake of that one quick and dirty solution. The case of this was written up in the article when the first guy to do this published the plans for his model. This was some time back in the early to mid 70's as I recall.

So yeah, fully trimming a precision pattern model is not about science so much as it is about the Black Arts. There's science behind it but I defy anyone to have come up with the solutions that are popular in the PP community from a purely analytical beginning. Too many of them are stuff like this "add incidence" trick.

Some of this has been lost to time as well. I gather it's normal to set up mixes and mode switches to provide such cross couplings that are needed for different flight modes and select these trim modes multiple times during each flight to suit the maneuvers being done.