here is the problem many current Hass H user run into
their lens are good, but not great (okay I have heard a lot of good stuff about the 100mm, but I am still using the CF 100mm f3.5 and believe its one of the best lens ever made)
I bought the 150mm, but sold it and decided to stick with the CF 180mm for now...
honestly MTF is a fair reference but thats as far as it goes, it tells little about the quality of the lens as it is missing a lot of the aspects
the 250mm SA and 350mm SA are of the finest tele lenses ever produced(not that I owned one but I was thinking about getting it so I did my homework)
I would understand if you dont like the HC300mm
but if you are still not happy with the SAs, then you need your camera checked, something has gotta be wrong