When I was trying to measure the strings I have, the thought came to me, "How do I get an accurate measurement of this puppy?" "Do I try to stretch it out or just pinch the end loops?" "Do I measure to the outside of the string at the loop or the inside?" I ended up pinch the loops using the TLAR method (That Looks About Right) and measuring to the center of the string. Didn't figure 1/16" or 1/8" of string length made much difference when we're talking 3-5" lacking in BH.
Technically measurement is suppose to be made under tension from the outside of a 1/4" dowel to the outside of a 1/4" dowel on the other end +/- 1/16". But I would say you are correct - 1/16 to 1/8" should not make any difference in a traditional bow string.
It would probably be a cheaper adventure to purchase endless strings while you find the right length for these bows. Once you have the length nailed down then work on either making your own Flemish string or have someone make a set.
I do have some old B-50 brown laying around here somewhere. I'm sure it is past it's shelf life, but it has been sealed in an Amber bag. I will test it this evening and see if it will make a safe string. If so, I can make you some endless string both to AMO 66" standards and then to what I personally think an old Bill Stewart designed bow would be. Might at least get you set on what string length to order or build next time
