Ok I bit the bullet and ordered the Dowelmax. It should arrive by next
week and I will be able to give an update of how it works out. I
pulled out the dial calipers and checked the bushings on the other jig
and they seem to be concentric. I am convinced that it will never line
up well with only the center bearing (threaded rod) to support it and
chose to get a refund rather than exchange for another one. I think
the self-centering design is better suited to edge-gluing thick panels
than what I am using it for. You would plane those after glue-up
anyway.

My plan now is to fill all the holes with glued dowels and cut them
flush rather than cutting fresh pieces of lumber and starting over, or
attempting to glue it up as is and then plane away a good amount of
stock hoping to get it to look anything but horrible.