Good work, Greg. It's refreshing to see that some people, at least, are
still willing and able to do this rather than unquestioningly accept
manufacturer's data. Even if the data turn out to be accurate, the
process is truly educational.

The varying SWR while terminated with 50 ohms is consistent with the 45
ohm Z0 you observed. My piece of BuryFlex is right at 50 ohms, but I'm
not too surprised at this amount of variation given the foamed
dielectric. I measured 80% velocity factor, so if our respective
measurements are good, the velocity factor of your piece should be
around 72%.

Roy Lewallen, W7EL