What were the symptoms? Often planes climb too much and people think they are tail heavy when all they really need is down trim. If you move the CG forward then you may not need down trim and you think you have solved the problem, but you would have covered up a problem that could have been corrected and created a better trainer.
I am a club instructor and sometimes I have moved the CG forward and corrected a problem, but in those cases the student had not checked the manual and did not know what the CG was supposed to be. I have also set up many a docile trainer with the CG at the correct place and not at 25%.
Tail heavy means the plane is unstable in pitch, i.e., if you give say, down elevator and release, it will keep going down or even increase the steepness of the dive; so you give it up and now it keeps steepening the climb. In this case, the only correction is to move the CG forward. But that is different from just climbing too much.
Kit and ARF manufacturers are generally very conservative with their CG recommendations, so if it balanced properly it probably does not need more nose weight.
There is no "one size fits all" CG. It depends on the wing area/stab area and tail arm/wing chord. This is physics, it's got nothing to do with "PC". The manufacturers usually err on the nose heavy side to begin with in my experience. However, for some reason many kit and arf airplanes need down trim. They shouldn't be designed that way, but they often are.
Jim