18x9 track wheel recommendation
 

I’m currently running 6UL 17x9 +42 wheels without issues. Looks like I’ll need to upgrade to a BBK requiring 18in wheels.

I’m likely to stick with 6UL, but are there any other wheels aside from RFP1s in the same price point with similar performance characteristics?

I've been following your brake problems. I wish I had an explanation for you but I don't. I do have plenty of experience with the same kit you currently have though.
You don't have to run 18 inch wheels if you don't want to. Check out the fitment guide on apex race parts website. I'm running 17x9-in Wheels with six piston calipers and 355 mm rotors.

Which brake kit are you running?

I was told I’d need 18in wheels with any of the Brembo kits with 355mm rotors. Interested to hear your setup.

Essex kit with 9660 calipers. Probably not what you want to hear, I know.