"Not wanting customer gonads to glow in the dark..."

Simple, lead athletic cups. Like the ones you wear fro sports...

OK, joking aside, to find out if my plan will work you need some actual capacitors to pad that LOPT collector. Then along with the HV output, watch the duty cycle of the pulse on the collector, it should be somewhere around 20 %.

I just looked up the PAL line frequency and it is not lower than NTSC. We expect 12.5 uS retrace pulse so that is probably close to what you need.

HOWEVER, since it is a monitor and has no need for a back porch for a color sub burst, it may be shorter. The design seems like the engineers were conscientious, and shorter retrace is usually more energy efficient. Since these units were made to run continuously they may have made it their concern.

It is not easy to tell if the retrace is as intended. One way is to use the horizontal phase, as you said it was off. If you return the control to its original position and padding brings it back within spec then you are getting there. Another way is to temporarily reduce the B+ and turn up the G2 to reveal overscan hidden by blanking, and that is a bit subjective.

Modification is fun ain't it ?

And my question stands, the core. Can you see it and if so can you slip a piece of say, card stock between it and the molded part ?