So, are you using a dial indicator and moving the hub as the JB dries to make it straight? Making straight prop hubs is my nemisis. They never seem to run smooth unless I have it to a couple of thousandths and use a balanced prop.

Tapers are not a big deal. set your crank between centers and use a dial indicator to set up the compound feed. Put sharpie marker on the crank taper to check you progress. It will rub off of the tight spots during a trial fit. Do not remove the hub from the chuck until all the boring is done.

I have thought of machining the outside of the hub, on the crank, in the lathe with the steady rest on the bearing. Then use a stud made of all thread that is glued in place with JB and pushed in to exact alignment. Is this the only way to get it perfect?