[bodywerks]

I sure would like to know what constitutes a loop for some people! I am baffled as to how many people complain about this, and I have never had such a problem in 20 years of flying, even with a plane that is not laterally balanced. Are you just pulling back on the stick and watching what happens? How quick are you trying to make the loop? How tight? If you consider 30 degrees low rates and you are using even one-third of that throw to do these loops, then I would say you are trying to do extremely tight loops. Airplanes with airfoiled stabs don't need much throw for most types of flying - a snap only takes 10-12 degrees. A loop, even flown pretty tight, only needs 5 degrees.
Yes, lateral balance and equal stab throws are also very important, but execution technique is also crucial. Many fliers find that they are accidentally also inputing aileron when they pull swiftly back on the right stick. Is it possible you are doing that?