I would contest your theory of not even measuring the wingspan. Just for a simple reason called, unproportional adults.

I am really close to 5'10" but my wingspan is 73 inches, or do the math, 6'1".

Since it doesn't take a math degree to figure out the length of your wingspan, just another person who is able to hold a measuring tape, I think your best bet would to measure out your wingspan and divide by 2.5

An even better way would to go to a pro shop that understands what they are doing and get fitted by them.

But then again, those are hard to come by in itself.