Thanks for all the comments. Couple responses:
The black 'engraved' line is indeed drawn by a pen for the purpose of 'demonstrating' an engraving process. I use the pen often to proof new programs. I have not had time to build my tail stock yet, so cutting on the unsupported end of a foot long tube would probably not be successful. The engraving video actually was done with belts set for high speed, but it still made pretty smooth curves. The 'backgear' setting is specifically for high accuracy (very smooth arcs) and/or high torque (drilling, trunnion table, etc). I am discovering that Mach has 'issues' with simultanwous 4 axis motion.
The tail stock will be built from a standard spin indexer and have very light duty ball bearings and a 5C collet. In this way I can pas stock not only the 4th axis spindle, but also the tailstock and work on very long pieces. I have an adapter from straight shank to MT3 that can be held in a 5C collet and then use 'normal' tall stock tooling. The tailstock spindle will have a conventional handwheel advance for drilling, etc.
As mentioned in another post, the shaving operation is really most usefull for internal stuff, but that doesn't make a very good video, so I just did something external and simple again for demonstration. Many of the videos on YouTube make me want to slash my wrists, so I really try to keep mine short and reasonably interesting.