Winter wheel setup - offset/spacer question

For those of you running 20" wheels in summer and either an 18" or 19" winter setup, are you using crazy large spacers to help "fill out" the flared fenders? By my calculation from the OEM rims/offsets, going from 315 to 255 rears (using either OEM 18 or 19" wheels) leaves about 38mm of extra space/clearance between the wheel and fender, which I'm guessing would look strange. Can you even buy spacers/adaptors that large (or are they safe???) Or do you just go with an aftermarket rim with a much lower offset? I think the OEMs have an offset of +25, so that would mean going to a negative offset to get close to the same exterior look.



Any pics of your setup would be appreciated.