Originally Posted by
Leisesturm
Even with calipers, the rule is to measure three times and average the results. I don't know all what is going on here but it seems to me like ID measuring the seat tube would be a start?? Why has this not been done? Until it is done there isn't much point to all the speculation.
It's often not easy to get a good measurement using a caliper on the top of a seat tube, as it can be distorted by the clamp. You really need a bore gauge to get a good reading on the tube below any distortion. Or just measure a seatpost that's a good snug fit.