JF, thank you for that, and I can certainly appreciate how that works for aeroplanes with a large speed range.
Thinking back to the Chipmunk, which has no tabs, except for the fixed, ground adjustable one on the rudder, then it does seem to be a touch of the black art or maybe devine intervention that gives the delightful 'Oh! I have slipped the surly bonds' feeling. Oh for a bit of devine intervention to get my hands back on one.