Thanks for bringing this topic up. I was thinking about this very topic the other day-is there a point of diminishing returns for VHF/UHF, where feedline loss outweighs any increased advantage in height you get. Sounds like there isn't.
Along a related line, how does increasing height play for HF, especially for lower heights? If you have a tribander miniyagi at 15 feet, which I know is too low to be really effective but that is where it is, would raising it to 25 feet really increase performance? It is still below a half wavelength high on 20 meters, but would that extra 10 feet of height significantly improve performance on all of the bands?
73 John AF5CC