Thx for the vote of confidence Mv8.
My new shiny shaft/tube arrived today. Instead of cutting it in two and adding a bearing journal I may just slide the bearing on from one end and fix it in the middle somehow. End fittings can be welded as was suggested (press fitted to the tube and all), but with some
means of removal yet to be determined. I'll use either a 1.25 bore bearing and cause enough clearance to push it to the right position, or I'll start with 35mm ID and cram in a shim to center it on the shaft. Mounting it to the frame is really fairly simple; two parallel fine threaded studs with nuts under a two-piece bearing retainer sandwich to snug it up, then two more on top. Clearance around the studs will let it self-align.
Here is another question I'm toying with: front (VW) brakes are hydraulic and I have all the stuff to connect them, etc. The rear is mechanical linkage, normally direct to the pedal on the right side of the bike. I could use a hand lever to actuate this in the car but I don't like the idea - no balance. Or two brake pedals working in unison
. Not good either. Maybe I can rig a small hyd. cylinder on the rear linkage, along with manual for parking.