Cheers man.
I obsessed over wheel width and offset before I ordered them as I wanted to get an 18" wheel and a decent sized tyre on it.
The FWD cars have a narrower rear track than the AWD cars and I liked the look of pushing the rear wheels outward a little - previously on my last V70 and, prior to that, my old 850T5, I ran rear spacers and extended wheel bolts (I dont do spacers with studs pressed into them). As I was having wheels made to spec anyway, I ordered these from Koya made to exactly what I wanted.
So, ET36, will give me a 12mm wider track width, than I'd have had with ET42 wheels all round.
You could also increase rear track using a set of C70 trailing arms.
ET60 wheel +20mm spacer gives you a net offset of ET40 (you'll need wheel bolts that are +20mm as well).
