[jjfritz5528]

Well, I did some testing, using a resistor decade box. Started with a 1k ohm resistor in series with the Shadow meter (as shown on the schematic) and reduced down to 15 ohms in steps. I got the same voltage across the meter, regardless of the resistor.  It was approx 4.5V to 6.0V.
SO I removed the resistor completely. I do get a good variation in the shadow width while tuning a station. Made some very minor positioning adjustments to the lamp.