Mike, I put one heavier spring in the mech weights. The strobe was to hard to read at such low frequency.
The test start at 375 dist rpm. If you look closely at the better videos, you can see the distributor machine arrow strobe start at "0" and top out at 14 degrees.
The video without the vacuum advance being addressed shows no rotor movement, and also shows how the shaft out of the distributor retards 14 degrees.

The video with vacuum advance shows no rotor movement with 14 degrees of mechanical advance, then adds in another 14 degrees of vacuum advance. This is where the rotor position moves. You can see the strobe arrows move to 28 when the vacuum comes in, but no movement from 0 to 14 with mechanical only.