[husker boxster]

The proper sizes you need are 8 / 45 & 9.5 / 46 for width and offset.

Porsche makes separate sizes for Box / Cayman, regular 911, and wide body 911. The sizes you've found are for a wide body 911. Some want the ultra-wide 11" wheel on the rear wheel for looks, but the only way you make it work is a massive spacer that won't be your friend on the track. Plus, you'll need to "adjust" / roll your inner fenders to accommodate that wide tire.

Your best bet is to find a set of lobster claws for a Boxster / Cayman in the sizes I listed.