A friend got a panamera 4, we are trying to figure out what would be an affordable option for winter-only wheels without going to ricer crap or paying porsche through the roof for the second set of factory wheels?

would boxster/cayman wheels fit? smaller/narrower is obviously preferred...

 

cheapest is to pick up some OEM 18" take-off wheels (from tires shop or ebay) and mount new Pirelli winter tires on them. Should be able to do it for less than $2000. I did mine with TPMS so I pay little bit more.

not sure boxster wheels will do as tire sizes for panamera is 245 front and 275 rear for 18".

 

yes that is what we are leaning towards, although having 9' wheel in the back limits winter tire choices (basically, just the pirellis you mentioned).

i wonder if front wheel with 1/2inch spacer would work OK in the back without looking too weird

 

^don't do anything funny. Just go with the stock setup without spacer. I am a firm believer of stock setup. We will not know more about the car than the team that designed and built it.

Besides all winter tires are cheap anyway.