umm...as far as i know it it will all depend of your offset.
just because you have a 10.5 rear width doesnt mean it will for sure stick out. you can have a 10.5 +40 and it will be "sunken" in more than a 10.5 +15 or so.
it seems the "usual" offset for a 10.5 rear is about +25, so list your offsets and people will be able to help you better
post pics asap, im interested to see what 19" re30's look on z4