2004 e85 non-M - ESR CS15 Staggered fitment

[synz4]

Hey all! I recently bought a 2004 Z4 e85 and I’m trying to find what size wheel with what offsets I should be buying for a staggered direct fit setup. I think I’m good with the 18x8.5” - 235/40-18 front and 18x9.5” 255/35-18 rears. What I am unsure of is what offsets I need with what’s available for this specific wheel (ESR CS15) and if I need spacers? I have checked around and different sites seem to suggest different numbers. I’m crap at racking my brain around this sort of thing so any help on which of these options I should buy would be much appreciated!!! Thank you all!

https://esrwheels.com/products/cs15-matte-graphite?_pos=1&_sid=6780d10b7&_ss=r&fbclid=IwAR13tKY7w9qI4L2Irmz_Y9eUoYdg5ACIUvOO0hurd10-lRO1M0HZ6UF7ZSA

 

[Panta Rhei]

You want 265 at the back not 255 on 9,5J. Plus 265 comes better with 235 at the front.
Second thing is that I am on Eibachs + Front rims are 8J ET 37 (so like OE wheels plus 10 mm spacers) and I do have rubbing issues on plastic fender.
Going for 8,5 ET 35 will rub for sure with tyre 235.
E85 model is a nightmare when it comes to spacing front because of bumper/fender design inside wheel arch.
ALpina roadster S was using 19" wheels with 235 tyre, but they equipped if with ET 50, not 35.