if I'm too far off base with any of this someone feel free to correct me, but afaik the "jello effect" in videos has 2 main causes:
1) vibration of the gimbal/gopro in flight.. this can be due to high winds, prop imbalance, or other factors that cause a physical vibration that is more drastic than the rubber dampers can handle. This is a PHYSICAL problem
2) VIDEO effect: in bright sunlight with no ND filter, it's actually the sunlight coming through the spinning props causing this effect. I'm not sure what other factors contribute here (if it's only when the sun is up high above you, not at like sunrise/sunset; or facing towards/away from the sun) but the only solution to THIS is a ND or some sort of filter on the gopro.
all that being said, achieving neutral balance on your gimbal is never a bad thing. just add a tiny bit of counterweight to the opposite side of the gopro from the side that "drops". I personally used a stack of tiny bits of duct or gaffer tape rather than trying to glue weight on
