Try this with your Hill or other ASL...
Start at no more than a 5.5 in brace height, no string silencers, and work up about 3-4 twists at a time. While most ASLs will tolerate a wide range of brace height and still shoot quiet with little vibration, they will definitely have a narrow range where they are just dead in the hand at the shot. I have ASLs from Northern Mist, Miller, Hill, Two Tracks, Schulz, Jet and Kimsha from 66in to 70in and every ones best brace height is somewhere between 5 3/4 and 6 1/8in. If anyone of them was better at 6.5in that's where I would leave it, but they are not.
Also I have noticed a ff string offers little advantage (arrow speed wise) on an ASL and prefer B50 for its better dampening characteristics. If your ASL is noticeably more shocky with B50 then it is out of tune. If you feel the need for string silencers, it is out of tune. All you should have is a low hum with B50 or a slight twang with FF and almost no vibration. I do use a little wool on the string (after tuning) to just about completely silence a hunting bow. Again, just try this, you may find you like your ASL a lot more.