Looking at the great write ups on the double a frame alignment fixtures on here I wondered if the split clamp on the column is necessary. I can see it maintains the ability to swing the head but I can’t think of anything I would need to that for. Famous last words I know. My column is filled, solid or plugged so I can’t look down through it from the top but I assume it goes all the way through the column base. My thought was to fab a clamp frame to attach to that base with close tolerance bearings for the lower A frame and use a wider sleeved hinge to join the upper and lower A arms. Still thinking about fine adjustment to tune the alignment. Silly idea? I’m retired with more time than money and ha e a pretty complete setup for metal fabrication- welders, plasma, oxy-acet, cutoff saws, 4x6 bandsaw, grinders, forge and anvil. What I don’t ha s is a slitting saw to cut that column clamp. I’m in no hurry to start- hasn’t been an issue for me yet but I am shopping for screw length bits and there is that no money thing again.