The horn offset, especially on the elevator can have a big effect, especially on a profile that does not have a really stiff fuselage. Friend of mine built a mid-size Cardinal with a 40 on it. After the first season it quit doing decent square maneuvers. We tried everything, finally ended up trimming 1/3 off the flaps(it was a pretty light plane). But is still glitched badly especially on the 4th corner of the square loops. I was flying it one day and he noticed that in that corner the whole tail twisted about 20 degrees. The horn was about an inch and a half from the fuse. With some ground testing it was easy to see that any significant force on the elevator would twist the fuselage.