[gfm]

I am reading all your comments with interest.
There is a further consideration on toeing and heeling and the use of a crash/race gearboxes and that is the use of double de clutching on the down shifts (which I can't stop myself doing since learning to race the first FFords).
This is, Bob Pearson, the moment the gearlever passes into and out of the 'neutral' part of the lever gate, if your clutch foot releases the clutch and that coincides with a blip of the accelerator, then the appropriate shaft in the box is spun up to a higher speed (approx the revs of the new lower gear being selected), then the next ratio is selected with the clutch depressed thereby unloading the cogs in any case, without any real stress on the dog teeth. The engine will also be at high revs and a smoother down shifttakes place, particularly relavent in the wet for example.
It's must easier to practice and describe this while driving an old London bus than it is a late FF, but the sequence is the same.

Sorry, but there is still NO DOUBT in my mind that left foot braking techniques are still IMHO a blind alley for the majority of circumstances on the circuit. Cars (not Karts) have too much weight to transfer and too great a suspension movement in the main to make this technique necessary.
Be clear about this, if you are not a regular race winner, left foot braking will not change things one iota.