Can you beleive it?! I'm going to the track!
I've gotten a fresh set of Corsa IIIs for the bike, and now I'm gonna scrub them in a bit before I prep the bike for the track. I've found a new spot. It's pretty clean, has absolutely no traffic, lots of corners, slow speed, the runoff is not that great but okay for the speed. The road surface is just a tiny bit dusty, and the corners are sharp, 45 mph max. Overall it's pretty clean and smooth.
I went out and did 200 corners in about an hour and my legs felt like jelly, chicken strips were down to 8 mm rear, and about half that in the front. For the first time they are even on both sides, so I guess I have improved (on my right-hand turns). I discovered my body position was different when leaning to the right, so I corrected that, and it seems it worked.
I used the track presures (31/33) to scrub-in the tires, and there were no hot scratches afterwards on the tread (nooks and crannies).