Sticks,
I've been entertaining making a Hill bow recently and doing some research on the proper dimensions. I have two Hills, and got information from others who make the Hill style.
Riser lengths are about 15". Tapers are steep, 0.008"/in on the heavier bows and 0.006"/in on the lighter ones. That seems to be what gives it the pronounced "D" tiller instead of more circular.
I find that a 68" bow works well for my 29" draw, but haven't tried shorter. Most of the Hill guys would highly advise against going as short as 64" for that kind of draw though. But maybe if you shorten up the riser a bit? Also, since you shoot a Hill with your heel down, most find their draw lengths shorten up a bit.