I've had my car at Pacific Raceways for 5 track days and probably have 2 more days left before I replace my front PS2s. I am looking at a square setup as well and discussed my options with my service advisor Alex at BMW Seattle. He races a Euro spec e36 M3 and has been doing this a long time. He argued that without a square setup it would be necessary to do a lot of ssuspension work including sways to dial out some of the understeer. His recommendation was to go with a square setup for performance reasons and convenience. I got the same advice from Noah who works at Group II motorsports in Ballard. Noah is one hell of a driver and an instructor with the Alfa club. He took me for a session in my car at the track and got a good feel what the car needs. He took me for a session in his car and I could barely walk when I got out of the car due to the effect of the incredibly fast turns on my vestibular system.
I am in the process of getting a separate set of track wheels and tires in a square setup but it will be a while because the wheels I want will take a while to get here.
2015 f80 M3, 2010 GT3RS