I like the term "Knob hacking" , first coined by bitseeker

I used a cheap knob first, seen here on the sensitivity control, I used a 6mm drill down the collett to find centre, then drilled a 3mm, then a 6mm holes from behind. The red little Tek knob is 10.3mm in diameter, so I drilled a 10.5mm hole from the front but used a drill press at quite high speed, with a low feed rate. I used a 6mm drill to hold the knob (held on by its own grub screw)
I think I will try one of the bigger spare HP knobs next.
Below is what the counter settled down to after about 1 1/2 hrs with a GPSDO input.
I have been battling which plug ins can be used in which 'serial numbers' 5245Ls, as there was several changes throughout production , once I think I have it correct I will reproduce it here.