I found that with smaller .40 & under, the right thrust didnt seem to be much of an issue. Then with big glow & gas, it really shows up, the bigger the prop, the more right thrust you need. If your plane constantly yaws to the left, that would be a major indicator. Another thing is HA 3-D, that P-factor thing seems to do different things when in HA and hovers really show what thrust line changes can do. If you are banging one particular control all the time, thats the one you should adjust.