I do remember Emilio said that 15x8 would fit on NA without any need to roll the fenders.
But a a friend of mine uses a set of Konig ReTrack 32mm, 15x7.5 and they to rub inside of the fender now and then. (It's actually the car on the picture.) They are fitted with R888's.
And the ReTrack would after my calculations be a couple of mm further away from the fender.
I post it here since you sell both the rims.

\\Stian.