This report applies to a rear bearing on a 2006 Tribeca. Rear knuckles are of the same design as on 4th gen. and above for the Outback (which is 5th and above for the Legacy platform). One obvious choice for positioning the screw is the parking shoe anchor plate, on either side of the pin. The plate is reasonably flat and bolted through to the knuckle without air gaps. The second location is trickier. I ended up using the bottom mounting ear for the caliper bracket. There, you have to sandwich a shimming piece of metal between the backing plate and the knuckle. A 10 mm Allen wrench worked fine for this purpose. I believe it would be easier to use the tool on the front bearings, as the shield can be unbolted beforehand.
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The tool worked as advertised to remove a hub that had been in service since February 2006 (although in NJ and with under 120K miles). The pictures show the tool and how it is mounted to the hub flange.