As I understand it, a pusher propeller helps maintaining line tension when the plane circles counter clockwise, while a tracker propeller does the same when the plane circles clockwise (i.e., inverted). Now, as stunt and combat planes have to fly in both ways, does it really matter which way the lines are tighter than the other?
Thanks,
Haoyang
Well, it is too simplified understanding.
Yes, prop has torque which makes rolling moment, but it is task of trimming to remove it. We have flaps or trimming tab to put the wing to level and thus it does not make any difference.
The real effect is precession. The difference is mostly visible in second corner of hourglass where pusher prop yaws model out of the circle and thus makes lines tighter. But yes, you are right that there are also places where it does not help, because just opposite happens in second corner of triangle. Fortunately it is also trimmable (to some extent) with Rabe rudder.
But there is still one difference and that is precession in straight flight, precession of pusher prop makes pitching moment down - means the same direction like drag of landing gears and thrust line of motor over the wing line (as used on classic models). That must be counterbalanced by permanent elevator deflection what can make different force down or up wind. That can cause hunting. Therefore and with usage of mentioned trimming, normal prop is easier to trim and pusher prop does not bring any advantage. I know several fliers who tried pushers and went back when they found that model with pusher was more difficult (but usually not at all) to trim to its best potential.