I have negative stand over on some of my bikes. I focus on top tube length instead. Plenty of top tube length sizing guides out there on Google. I always tell people "you don't ride a bike like the Flinstones drove their cars." I came from the era (1970) where a small Schwinn was 22 inch ST, medium was 24 inch ST, and large was 26 ST. Wow, those were the days.
I've had smaller ST bikes with super long top tubes, like a 52 cm CTT ST, 58cm TT CTC, that was too big due to the silly long top tube. I use stem length to fine tune TT sizing. I've seen XL bikes with short stems, and small bikes with long stem. I would not use stem length to represent sizing. Realize these bikes are 50 years old, so even if they originally came with a long stem, over the years, riders could have swapped them out to better fit them. Heck, sometimes they didn't leave the original dealer without a stem swap.
Last edited by wrk101; 03-20-22 at 10:22 AM.