How do you feel about the RS-Pro's vs the 615k+'s? I'm looking at making the same switch as you just did and the two are similarly priced. It'll be my street tire/autocross tire. I have inspection in February and I'm not sure if I'll pass with the 4-5/32nd RS Pro's lol
Edit: Not looking to win tire class, just to daily on and have fun at autocross. Winning is a plus
RS-Pros were certainly stickier than the 615k+. The biggest issue i have is running them on track with an 8" wheel. While they are super responsive the outer edge and sidewall of the tire takes WAY too much abuse for my liking. Hitting curbs and watching the curbing wear down below the lettering on the sidewall was a bit scary. Adding more camber would likely help but i chose to just go with the wider section width 215 size Azenis.
This was my first event though and i did not get them heat cycled when i ordered them. So fresh out of the mold(28th week of 2020!!!) Azenis need way more than a few trackcross runs to scrub off some of the mold compound before they get anywhere close to the mid-cycle RS-Pros. The biggest thing i gained going to a 215 is the lack of sidewall abuse on the curbing at Summit Point. The grip will come after a few more cycles and i am crossing my fingers are equal to the RS-Pro.
Another you could check out is the Nankang NS2R. Phils Tire Service has them in stock now in 215/45R16. They are a bit more expensive than the 615K+ but are a newer compound 200tw and are probably equal to the grip level of the RS-Pro. Rivals are out there too in 215/45 if you wanna spend the big bucks for top tier tires.
TLDR: Section width will help square the tire off in a 215 vs a 205 tire on an 8" wheel. The RS-Pro has more grip than fresh out of the mold 615K+ tires. Waiting to get more miles on the 615k+ before i condemn them as behind the RS-Pro.