That could maybe work but it sounds like a risky prospect.
Maybe instead of just providing measurements, you use one of MrProper's specs as the reference? Given his Greek sculpture physique, that should account nicely for shoulder slope.
But if it fits his statuesque-ness well, I don't think it will fit my only-humanness well and I'll be in the same position I am now: with a jacket that sits on my neck rather than my shoulders. Which is a well-known Aero thing in general, but I'm hoping slightly slopier shoulders would help me out.