Have you ever measured it? Have you any idea of the magnitude of
current measurable at the shorted point in a stub during transmit?

No Cecil I don't, should I? The only experience I have with a shorted 1/2 wave
stub is in receive applications. I have swept them with a homebrew spectrum
analyzer and tracking generator and can say they look like series resonant
circuits. At the micro watt level will I still have several Amps in the stub?
How would you measure the current in the stub during transmit using equipment
the average ham (like me) has laying around the shack ?
73 Gary N4AST