Does the sticker inside the door give you pressures for that size setup?

 

No 18” wheels at all. That’s why I included the table from the owner’s manual.

 

The pressures are virtually the same for every tyre size listed. Only the RS is recommending slightly higher pressures, but are just + 3psi, not a huge difference. Just use the same pressures as for RS with 18" wheels--35 front, 32 rear.

 

My thought also. No need to overthink it.