Oh God, I can't believe I'm getting involved in this, but here goes. Should be in line with those that know though. I'm no expert, but I did hang around with a bunch for nearly two years of racing seasons (and I did stay in a Holiday Inn...
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I was on pit crew for a Grand Am Koni GS team for two years. The first year we had four cars, D. Law of Brumos drove for us, among others (Andrew Davis, Milner Jr., shall I go on?) so yeah, a bunch of guys that you could say knew what they were doing. I have seen first hand telemetry coming off the cars - they do not kick in the clutch at the end of a straight under braking. To the dude or whomever else thinks this is done and is the right way, I'd recommend going to find your source and thank him or her for being a complete dumb ass and making you look like one two.
I really wanted to address that A. Senna vid - is it just me, or does anyone else think he ends up with his heel on the floor board during breaking? I had to watch it a time or two but I think he drops his heel to the floor for a reference point, in addition to the high likelihood that he does swing that knee to the left to change the geometry at his ankle. This is what has worked best for me, but I still struggle with the "floating foot" with out my heel on the floor. If you're on the brakes as hard as possible then sure, that is as good of a fixed reference point as the floor, but lets face it, you're not always on the brakes 100+% and that is when I find I am smoother and more controlled under braking with my heel on the floor for a reference point.
In the Senna vid, it just seems like the shoe is always at the same height in the video frame that I wondered if maybe he did have his heel on the floor.