I decided the hardware was small enough to fit on 2 PCBs on the backside of the
VFD: one PCB for the 4094s and one for the rest.
The first PCB contains just the 4094s.
The second PCB is on top, containing the 3 diodes for the filament, the boostconverter, the voltage shifter transistors and the microcontroller.
In the middle is a sandwitched mess of wires...
And eventually, this is how it looked after I put in the initial firmware.