Just throwing this out... but did you mount both rear wheels or just one?
I ask because it's not uncommon for the diff to be off center.
Mine is shifted about half inch towards driver's side and I've heard of others as well.
I'm running 17x9 with 4.5" backspacing. (265 wide tires)
IF my diff was centered correctly there might be room for an extra half inch of rim. But it would be very tight.
I don't think re locating the hangers would do anything for you because your issue seems to be outside clearance, not inside...
I'd be hard pressed to go to the trouble of a shorter diff for just .5 inch more wheel.