A nice thing about the hobby is that if it works and you're happy with it, then it's good! I haven't been happy with either of my attempts to use mixes to fix an elevator trim issue that was related to throttle setting, either thrustline or speed sensitivity. If someone else does, there's not a thing wrong with it. I'll agree with you on the topic of initial trimming. It's a lot easier to get the plane flying straight and level at full throttle and then adjust things to work at lower settings than it is to get it right at mid throttle and then try to adjust to make everything else work.