[Boulevardier]

Not sure if I understand the exact geometry you've got with that valveholder. But I think I remember reading somewhere on the forum that a rough-and-ready way of getting a reading from a valve pin is to twist some thinnish multistrand flex tightly around the valvepin to be measured - making sure it's right up against the bottom of the glass envelope. Then carefully replace the valve, wire and all. You can then measure from the other end of the flex, and afterwards remove the valve to remove the flex. Don't know if that helps in your situation, but just a thought.

Mike