Tony,
we are talking IMAC,Sport planes ,and Pattern planes here,
.5 pos is only a starting point ,,many factors are included to find the right inc. airfoil ,wing area, overall weight of the airplane ECT, But thats a good place to start.
OTOH you never need more than 1.5 down or 1.5 right thrust on any modern pattern plane, no matter the prop size ,and,no matter who tells you other wise.
The engine thrust has almost no effect on trimming( if done correctly with the proper CG and wing inc.) and should be the last thing adjusted for trimming a pattern model.
and then only a very good flier can even tell the difference.
If you use the engine thrust to fix something you just broke 3 other things it`s not an adjustement you would want to use to fix anything. so,
If you have to use aileron trim or throttle to rudder trim , mixing for different model speeds your not finished trimming your airplane and your c/g is too far rearward.
don`t let no one fool you an that..
Engine thrust has been given too much credit over the years and just repeated from guys with little credibility on the matter. The Wing is the most important thing to adjust ,
CG is Second, other things next ,thrust, Last ,But if the design is sound , and the designer has done his homework,, then your thrust should be correct from the start,,unless the designer uses a .3pos, down to 0-0 setup, then he will adjust the thrust first and you have to mix the crap out of everything else.
This was used till a few years ago but most modern designs have started using some measurment of Positive inc. in the wings ,,,they just have not figured the rest out yet
Bryan