So I pulled the master cylinder and ordered a different model, having been schooled by @chines1 that the one I had in there, recommended by the PO with the universal endorsement of writing "USE THIS" in sharpie on it, is inadequate to the task of actuating four-wheel disc brakes. It was designed for front disc brakes and rear drums, as indicated by the single "D" on the end of its part number. The new one's bore will be 20.6 mm's in diameter, as indicated by two letter D's at the end of its part number.
I am advised that this will or should obviate the need for the 2-lb residual pressure valves and the unobtaniam brake line adaptors I have ordered but have no confidence in their being the actual ones I would need for this job.
Thoughts and prayers for me? Can I get an "amen?"
While awaiting these possible final keys to Full Spyder Viability I've set my attention on creating a valid and functional flat towing system for the car.
As many Spyder owners have discovered, the standard VW flat towing device can work, but it's a bear to get it fixed to the beam, which is so far under the car and then unreachably up in the body work.
On my car there is also an aluminum sheet screwed in under it, blocking access.
But since I extended the frame forward to render the jack points functional, and since I also installed 7/16 bolts through these extensions from the bottom of the floorpan, I have the built-in makings of a potential towing system.
All that's required is a sort of bracket or frame to extend from those bolts, past the jack points, to a spot under the grill. From there a simple horizontal pivot to the tow bar.
CAD:
It seems appropriate that the 1x2 box tubing I'm making this out of came from the same treadmill I fabricated the frame extenders from.
Holes for those big bolts....
Then measure again and relieve for the jack points.
Tomorrow I'll grind these holes out and locate these tubes in the box tubing so it fits over the jack points snugly.
After that it's tack, test-fit, maybe tack again.
Then I'll get some pins to fit through the fronts of these guys and gusset all that & tack it together.
And after that I cut the ends of a regular VW tow bar and make box ends to fit over the ends of these brackets and slide the pins through.