It would be quite nice to have the barloc index on the rail. For us neurotic people, keeping it square while achieving the specified "gap" is not an easy feat.
Shot my Nucleus today a little. I would disagree with running with authority, it ran great even slow. I think it is more important to run it harder forward than rearward.
I own both a go gauge and no-go gauge in this caliber (specifically because of the switch barrel setup).
Using a go-gauge with 1 piece of scotch tape on the back is acceptable as well.