Hi Sam, for lowering the frequency there are no issues other than entering the audible spectrum. I can confirm your results here.

Please note that the voltage regulator algorithm thinks that with increased duty cycle there comes increased voltage. If you’re seeing serious swings you might need to change it.

The tubes well shielded by design in regards to RF, but the counter circuit (PCB traces, components) are not. But I don’t think the high voltage inverter is of concern here.

Having two units is definitely the way to go here, and try to get the Ethernet running so you can automate the process.

Good luck!
Radu