I am sorry but respectfully, I am curious as to how you came to this conclusion?
the biggest problem I see is that many people fly them to small and the airplane looses energy more than them being to large?
I didn't come by the conclusion. I just read Wild Bill's 101 Stunt Planes. Some planes pull better in level flight and lose more line tension in the overhead eights. Yes WB simplifies some calculations, but they are quicker and more reliable than cut and try.
A lot of flyers, especially in Advanced, seem to like how the Pathfinder flys. It's a relatively easy build, doesn't pull hard in level flight(<10lb) and keeps 1/3 of it's line tension in an OH eight-3.2/9.45. It's easier to fly because the pilot doesn't have to contend with widely varying line tension. Compare that to the Chizler- pretty light level flight line tension, 6.6 lb and it drops to 20% in the OH eights. Both planes can fly very well, but the Chizler requires a much defter touch especially if it's a bit breezy.