Want to add another data point.
I have Black Boy and Indian Free (both from RT) planted next to each other. (Along with an Autumn Rose - renamed BB? - from OGW/Northwood Nursery before they stopped listing it - the AR turned out to be a mislabeled Galaxy peach.)
The Black Boy ripened 7 days after Indian Free. IF was +58 Redhaven for me. +65 for BB.
Pretty sure O’Henry is supposed to be +40 or +41 to Redhaven, (@Olpea look right to you?), which would make your IF +51 or +52.