I expected to have to brace this underneath the table top, but surprisingly this is extremely rigid in the vertical plane. The rail on the end of the table is about 3" wide, and seems to provide a sufficiently large bearing surface that the vertical plane is actually the most stable. The moment-arm around the point where the guitar body is held does allow the end of the neck to wobble around just a bit, but won't be a problem at all when applying finish with a brush.
It needs a little tweaking, as the "brake" on the end isn't quite as secure as I'd like it to be. It certainly isn't going to suddenly come loose, but the rubber that I attached to the pipe with CA glue is actually allowing a bit more oscillation around the horizontal support than I'd like. I'm going to attach a wood disc to the end with a pipe flange, and drill indexing holes to allow the support to be rotated and "locked" into any position.
The best part is the mounting to the guitar body. The brass bushing is glued into the oak block with JB weld. Before attaching the 1/4" pipe nipple on the right-angle pipe assembly into that brass bushing, there are two 1/4-20 set screws running at 45° in the ends of that block that tighten into the pickup cavity. The right-angle pipe assembly then attaches to the horizontal 1/2" galvanized pipe support using a union which tightens up just fine by hand.
