I went to a square wheel and tire setup for track use a few years ago and have used 3 different square tire setups now. I have 6 wheels, so I mount all 6 and rotate them front-rear-off so they remain relatively balanced on heat cycles. That allows me to have spares in case of mishap, and also to run them until they cord. Also relevant: current geometry is -2.7 camber front and -2.2 camber rear.
My wheels came with BFG Rivals (4 tires, two wheels in boxes) which were used for some autocrosses and about 3 track days. They wore at the inner tread blocks even with predominantly track/autox use, and never felt anywhere near as grippy as the RE71r's I had used on my stock wheels previously. They have been superceded by the Rival S and Rival S1.5, neither of which have a load rating that meets requirements for the 1M.
Last year I used 6 Toyo RA1's (TW100) rotated as described and got 7 track days out of them.
They were heat cycled but NOT shaved from the Tire Rack. When new, they were very squirmy from the thick tread blocks, but as they wore they became brilliant. Their reputation is that they get progressively better until they cord....I confirmed that! Even with my alignment, they corded at the inner treads, which surprised me.
This year, I decided to try the Goodyear Supercar 3R which also has a TW100 because it appeared to have a more stable tread pattern and I hoped they wouldn't be squirmy when new. That proved correct, and they were grippy (good for lap times 2 seconds faster than last year in similar conditions), BUT I delaminated 4 of the 6 tires by the time I had done 11 sessions, about a day and a half. The outer tread blocks were gone. Inner tread blocks showed very little wear. It seems these tires wanted a LOT more negative camber. This was despite targeting hot pressures of 43-44 front and 42 rear which the T1R thrived at. I had temp readings to confirm that those pressures were spot on for the RA1's last year, but did not have access to a pyrometer this weekend. Because I was fully expecting to get a season out of them, I rotated them each half day for the weekend to get them all scuffed in. Sunday morning, a front tire delaminated on its 3rd session of the day. I thought it was a defective tire. I replaced it, then started watching closely. I replaced another (other front) after the 1st afternoon session. After my second afternoon session, both of the tires on the rear at that time had signs of starting to delaminate all the way around the outer edge. I drove my sons Rx-8 for the remaining two sessions. (Always bring extra tires, and in case that fails, bring an extra car, can I get an Amen?)
I'll post some pictures later.
So, now I look at my options. RE71r has gone extinct. Rivals don't meet load requirement. I would prefer to stay with 275 width so the options Direzza ZIII or Falken Azenis 615 or 660 if I want a "street" tire. Everyone agrees RA1 is better than R888 if going the tw100 route, and I have heard good theory that they may last at least as long when shaved, which would eliminate the squirm when new.
If I drop down to 265 width, there are a few more options including Hancock Ventus V12, Yoko AO52, PSC2 connects. Not sure I want smaller tires especially at the rear.
What says the hive mind?