Stabow,
Wingspan gives the overall arm length. Of course we vary in draw, like there may be some difference on left or right side. If someone have a 78" WS vs say a 69" WS the draw should be quite different. I am of course looking for Hill style longbows. Different styles of bows will change the draw due to grip or thickness of riser. Just wonder is there is an average for those that shoot the hill style longbow. BTW: Interesting that Great Northern sizes there bows by bow length to match your WS.