Replied to PM.
I'm always impressed by your clear photos. After feeling the clearance with the cap screwed onto the column with grease lubrication, I think I'm going to switch over to Teflon tape as you advise. I, too, would add some pad between the lockscrews and the pipe threads. And regarding disassembly and transport, I fully intend to take the legs off and remove the cap w/mount from the column. In fact, I noted in some other forums the contributors talking about the formidable task of climbing up on ladders and screwing the cap on, I assume with a large/heavy telescope installed.
I'd always assumed coupling the tube to the mount was the final step of assembly, especially if it employs a yoke and straps which must permit positioning for balance and viewing convenience. In mine, the user must make a choice where to penetrate the tube for the mounting bolts, thus constraining it axially and rotationally. I'd appreciate some comments from readers about choosing the position of the tube on the mount.
Here's a further update on the repairs. I completed the elevation axis shaft today - it fitted the head casting nicely at about half a thousandth over 7/8 inch diameter. I also sawed out a blank for the tangent arm and profiled it on the mill. With the shaft now completed, I'll finish boring the arm for a snug fit, then drill and tap for the setscrews. Will provide photo then.