Ken,
That is really COOL. So, now I'm curious, having seen your previous post with the pictures of your jigs and processes, Did you do something similar with hexagon ends, but forego the drilling and indexing pin process to do the square blank or did you still go through your drilling process but just with a square blank?
Parts of your process are very similar to what I do to trim the edges from my blanks before I take them to the lathe. I essentially use the turning bushings to clamp the blank onto a 1/4-20 drill rod that has wooden octagonal blocks on either end. Then I use the blocks against my bandsaw fence to trim off the excess blank leaving an octagonal shape just a tad larger than the largest bushing OD, perfectly squared with the tube. It really sines when I use an odd sized or odd shaped blank as the blade is referenced off of the centerline of the tubes.
Dave