Having owned a Don Brown longbow which was a Hill style, a Schulz made bow, and I still have a couple of other Hill style bows made by now deceased direct disciples of HH, I have made a few observations.
One is the grip type is big determining factor, for more comfort I prefer a full grip vs a thinner dished type. Brace height is another aspect that I have found to greatly change the comfort level, and as others have stated, >6.75" is about the point of being the most comfortable . Higher arrow weight is absolutely paramount to how well the bow shoots. Finally, over torquing the grip will almost always make for an uncomfortable shot. None of this is unknown to most on this site but I think that these observations, if ignored, can make for a disappointing experience when shooting a Hill style bow.
To me, Hill style bows are analogous to driving a heavy duty powerful truck that lacks power steering and has an unassisted manual clutch and tranny . Unabashed power but you have to accommodate it as it won't accommodate you.
Finally, I do agree that the D style longbow is the pinnacle for absolute "pick a spot" style shooting. Just as a finely made double gun goes where you look, a Hill style bow seems to want to to follow the eye to the target.
DD