Congrats on the purchase, and welcome.
I own an MKI, so I may be wrong in saying this, but from what I've read up on wheels 17s are big, but 18s are too big. Maybe a 16/17 combo would work a bit better? I don't know, but for more of a specific answer I'd refer you the
Wheels - Tires section, but I noticed you already beat me to it,
Custom Wheels What to do.
As it is said on the interwebz - Pictures or it didn't happen

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