Both Right Gear and Axle as well as The Hollister Road Company use a rotor equivalent to NAPA # 86830 which is very very similar to the rotors that came on my late model axle but these have a 4.641" bore (measured)
The Bendix brand I have here measures 4.63" which is obviously different than 4.641. The reason the tolerances are so different is that having axial run-out doesn't affect braking on a Disc the way it does a drum. Lateral run out on a drum doesn't affect braking the way it does on a Disc. So a few thousands on a disc to hub fit is not as critical as on a drum. If its to far out you could get a high speed vibration in theory. Disc rotors expand when hot so you do need some room for them to do that on the hub so a .005 fit is not a good thing in this instance.
As for the Right Gear adapters they no longer make the kits and have no idea when they will again. I tried to purchase their cad file because they had no idea when or if they would do these again, but they actually subbed it out and had no file, this was as of last month.
Were I doing the larger bore rotor I would used a centering ring to make it hub centric rather than lug centric but not as close as your thinking.
Rings Link to hub centric rings
