I did not check the rpm, I would guess 1"/sec. at the cutter. A too strong cut would slow the rpm and give time to back out the router. One 1/2" x2" carbide inserted bit did the job. Depth of cut was about 1/2". The logs were pretty dry Douglas fir, cedar would be softer and probably last longer.
No idea on the 18"x25'. A center roller rest could be added with a fabricated ring fitted to the log. They must have had some intermediate rests for a 60' mast unless it was for a ship-of-the-line!