My thought is that if someone has, say, 42cm wide shoulders versus someone else at 38cm, when we get aerobars and pads set up for fitting, we can at least predict a comfortable starting point within the range afforded by aerobar manufacturers. The 38cm wide person would start narrower. I would think that it would also be influenced by how far apart the hands are on the extensions, length of forearm, and length of upper arm.
Maybe I'm just really complicating something simple or maybe I'm ignorant of existing solutions, but it seems to me that we could quantify this. Maybe a formula like arm pad center-to-center = (shoulder width + aerobar extension center-to-center)/<some factor>.
We've got F.I.S.T. formulas for the X and Y planes, but how about the Z plane?
Any thoughts are greatly appreciated.
Vector Cycle Works
BikeFit Instructor | FMS | F.I.S.T. | IBFI
Toughman Triathlon Series Ambassador