Hi Richard,
it is possible to fitting the 11" wheels with offset 47, but you need 15mm spacers and 265/35 tires, also the rear fenders must be modified and you need a negativ camber of -2,5°.
On my own Boxster i have installed 8,5 x 18 and 11,0 x 18 with 225/40 & 265/35 with a lower -100mm suspension and it will fit perfect. but keep in mind, there´s a lot of modifications to do.
