Finally getting back on track with the CAD/CNC stuff! It appears that the problem with the CNC router is the tech who came and "tweaked" the machine was a little overzealous in removing the "slop" from the stepper motors' gearboxes. Mind you, the machine was cutting with perfect accuracy, but he determined the gearboxes, especially on the X-axis, were horribly loose. As a result, the machine would appear to bang off a solid physical limit, while machining in 3D (lots of quick direction changes, and constant movement). He eventually offered that area of his professional services as a possible culprit, and suggested I shut the machine down and try to manually push it in the three axes - I had to put a LOT of effort into moving it in both X & Y axes. Then, it would let go, suddenly freewheeling. My guess is this is what was happening in machining, and the hard, audible/visible, bang against the imaginary limit was the stepper motor catching again and basically snatching it out of freewheeling - but out of position (original origin).
To test my theory, I painstakingly machined all 38 of these little slices one-by-one, limiting the machine to a small area, and at fingernail-chewing, thumb-twiddlingly slow, speeds; to allow it to remain "connected". It worked, and perfectly. Two days (twenty-nine hours of machine time) later, I walked away with the rear stringer for the rag top.
(I didn't actually sit in front of the machine that long - I would program/setup a slice, start it, walk away, and come back later to start another...)
In the meantime, Riley, our new high school intern worked on the aluminum sheetmetal inner frame structure.
These will be TIG'd into a sculptured little "angle iron" frame, and bonded into the carbon/foam/fiberglass/aluminum composite "rag top".
I am going to run a couple air cuts of the window frames, and if the machine has loosened up enough to stay focused, or (if not) after we re-adjust the gearboxes, I will be able to cut them, and finally assembly the rag top frame. Schism really close to making the transition from a pile of parts to an actual car.