I got to thinking, so I went back and looked at my last several Hill bow specs. Here are a couple that are 66" with 13.5" risers. A bit light, but shows that Ben's numbers are quite reasonable. James, I'm not sure what you're looking at to make sure we're all talking apples and apples here.
Exhibit A: 0.524 total stack at the butt yielded a 44@28 bow with 0.005 taper and 0.043 glass, 1.15" at the fades to 0.47 at nocks.
Exhibit B: 0.536 stack w/ 0.043 glass and 1-1/8 at the fades yielded 50@29.
For reference that we're definitely in the over 1/2" stack ballpark: I also have dimensions on a Big 5 built by HHA. It was a 15" riser and 70" nock to nock, but was 0.0066 taper and 0.603 total stack at the butt, or about .59 at the fades. It was marked at 65#, but measured about 60.5@28 on my scale.
I've got a bunch more, but that's what is in front of me at the moment.
-Dave