One little thing to consider though is the lateral balance. Aircraft that are normally flown two-up (student + instructor) are trimmed to fly balanced in that configuration. If you then fly such aircraft solo, the lateral imbalance may require a bit of constant pressure on the yoke.
You can alleviate that pressure with the rudder (secondary effect) but then the aircraft won't fly with the ball in the middle. (And for the same reason, tweaking the rudder trim tab may not work either.)
The only proper way to address this would be to have trim in the roll axis. However, light aircraft such as the C172 are manufactured to a budget, both in monetary terms and in mass terms. So this is normally not installed: They only have trim in the pitch axis.
The rudder typically has a fixed trim tab, but there may be a fixed trim tab on an aileron somewhere as well, or the ailerons will have a different way to be trimmed permanently. But in all cases, as said before, this requires consultation with an engineer and possibly a series of test flights to get things setup properly. DO NOT tweak the trim tabs yourself if this is not your aircraft. And do not try to solve a roll problem by introducing a yaw imbalance.
Last edited by BackPacker; 13th Jul 2017 at 09:23.