For reference: 17x8 et 48,OZ Ultraleggeras fits my Blob wagon where the rears are narrower than the saloon. These wheels clear a set of Ksport brakes as well.
Best option would be to try them on the car if at all possible or if someone here or online has them already. There's a US website that has a lot of different wheel setups with fitments for subaru including pictures and whether they need arches rolled etc. I can't remember the name and I'll try to look it up on the desktop if I get a chance [emoji1417]