For cutting the yoke tenons, I used the technique described by Ty earlier, rather than using a filler piece in the top curve of the yoke.  Ultimately, this was both easier and more accurate.

Pantorouter setup for the tenons started with roughly centering the work on the table (front to back).  To extend the fence, I used a uniform thickness scrap long enough to contact the two small flat sections on the top of the yoke.   Butted up to the fence, this ensured that the plane of the tenon ends would be parallel to the edge of the table.

With a centering bit in the router and a centering pin in a loosely attached red template that could slide, I moved the centering bit until it was in the center of the tenon at the upper end of the yoke.  With the red template slid into position, I tightened it down.  I repeated the procedure to center a dowel template for the lower yoke tenon (I decided on a dowel since the end of the yoke there is patch only about 1" x 1"). The middle template was not used (I just slid it there to be out of my way).

With the templates properly mounted, I removed the yoke and replaced it with some scraps to test the setup.

With the test pieces still clamped to the table, I used the corresponding guide bushing router jig to cut the mortises in another scrap.

Testing the fit and spacing of the tenons.   Good fit!

With the fit verified, I put the yoke stretcher back on the Pantorouter, and cut the tenons (I removed the fence extension after the yoke was clamped in place).  I had originally allocated 3/4" for the tenon length in order to yield 21" span from shoulder to shoulder.  However, I had mis-measured the length of my yoke blank prior to cutting the yoke on the CNC.   This left only about 5/8" for the tenons on one side.   So I cut the tenon short of the original shoulder line on this side, then measured over 21" to mark the new shoulder location on the far side.  No harm done.

The corresponding mortise jig had been setup such that the outer surface of the yoke would be flush with the edge of the arms, which is how the original chair had it.  I believe it was placed that way to give extra room for the front legs to fold into.   Since mine won't be a folder, the yoke stretcher doesn't really need to be right to the arm's edge.  Once I saw how close the 1/2" mortise would be to edge of the arm if I did position the yoke that way, I decided to re-work the jig to offset the stretcher in from the arm's edge a bit.  The mortise will be further into safe territory and bonus, I won't have to worry about where to start/stop the 1/4" radius roundover that the inside edge of the arms will receive. 

To fix the jig, I plugged the existing Domino holes, then mounted the template back on the CNC and cut the newly-positioned Domino holes.

With some reference lines made on the arm pieces and corresponding lines on the jig, I could mount the arms in the jig and cut the mortises.

Time for a dry-fit progress shot.

Next up, I'll work on joining these two assemblies together.