Thanks for the compliment. I can't take credit for the design though, it's basically a ripoff of the Littleton Shotmaker.
The size of the orifice in the "dripper" does affect shot size. My first drippers had .024" holes (#73 drill) but the shot was a bit bigger than I wanted. The maximum allowed at my club is #7-1/2. My second drippers have .020" holes (#76 drill) and that is about right. At this point I have no plans to attempt making bigger shot.
Re a "way to start and shut off lead flow" . . . my shot maker does have that. If you look at picture #1 and #2, you will notice that the shot pan is in a level position. In this position the lead level is way below the opening of the drippers (i.e. no lead flow). To start the lead flow, I tilt the whole thing up at the back . . . look at picture #3 and #4 and note the position of the "stilts" at the back. There is a hinge at the front, so while this setup may look flimsy, it is safe and works perfectly. Someday I want to make some kind of lever arrangement to do the tilting. Winter project.Re PID . . . not sure if it's necessary for shot making. My heat source is a 1000 watt electric element from a Can Tire single burner hot plate. I use the simple temp control that came with the hot plate.