If you are going to experiment, you must determine how your model is currently configured before you start changing things.

I suggest that, for convenience, you take the line of the horizontal stab as your reference. Measure the existing wing incidence & engine thrust lines relative to that, then change only one thing at a time while you are experimenting.

Make your changes small & easily reversible -- for example, change wing incidence by shimming the leading or trailing edge, at the wing saddle, with popsicle sticks to see what happens -- then it is easy to go back to the original config. Same thing for thrust lines --shim the engine mount with thin, easily removable shims.

The changes will be interactive. If you change the wing incidence you will get a particular result -- same for the engine thrust. If you change both, the result will be different from either of the others -- the process is itterative.

If you find a set-up that works better than what you currently have, you can make it permanent when all of your testing is completed.

Good luck & have fun.