Before I do, a brief pictorial recap on the original conversion:
The original motor switch was a large white panel mounted switch, spring loaded normally open, which I cleaned as best I could during the original conversion. Replacing the switch was difficult because of the physical size of the switch and the associated cutout in the front face of the Tx. When flying my Cardinal & Weekender, it served well. In hindsight, both models were relatively sedate, so changes in motor setting were 'casual' & tended to be well spaced out.
However, I fitted a new motor to the Weekender which made it very zippy and lovely to do aerobatics with. With full power it climbs away at a constant 30-40 degrees, reducing to a speck very quickly if left uninterrupted. Medium power emulates what it used to be like at full power

I went through my box of switches & found a small micro switch which looked like it would fit inside the original switch housing. Judicious use of a sharp knife and a fine routing bit in the Dremel had the micro-switch fitted relatively quickly inside the old switch housing.
Now the switch action is light and positive - I plan to test fly it on the weekend.