[BAracer]

Re-watched the Triggerman video and did another reset on the Hudy and, blimey, I found the adjustment. There is a very small amount of movement in the centre block, and the feeler gauges he uses are not chosen by accident. The movement IS that small. 

Anyway, played around a bit, and re-rubbed the test tyres for each adjustment, and I think it is almost spot in now.  



And with a bit of searching, I discovered the big knobs are actually made by Triggerman.