Steve,
Thank you for posting this.
I watched the video with interest but was left with several questions the man didn't address.
One of these is the use of a dowel pin to be placed in one of two holes at the bottom of the device, after which a quadrant [made in brass for some reason] was moved into contact and locked. It wasn't clear what this achieved or why it was considered necessary.
The radius arm that rotated the fixture was anchored back to a firm mounting to the side of the shaper, but no allowance was made for the errors introduced from the arrangement; a form of Watts parallel linkage was surely essential.
He spent a lot of time showing how the device was machined but the critical details on it's working were skimmed over too briefly to follow.
Intriguing but it left too much unsaid and in the final closing words we were told there were inaccuracies arising from the lack of bushes at the ends of the radius arm as if that explained away a fundamental design fault
Regards Brian.