I don't doubt that slight engine thrust angle changes will have a trim effect on some planes but in most cases having the correct CG and lateral balance along with taking the time when building to make sure that the wing is level and straight with the stab and the stab is 90 degrees to the the fin will usually then require very little surface adjustments. Let's face it, a plane doesn't have to be perfect to fly or none of them would. I'm not knocking your method, but I personally don't know anyone that trims a plane with engine thrust angle, even the old timers in our club.