As the Nobby is scale sail, I would use braided Dacron. Monofiliment fishing line works well but looks out of place, IMHO.
Many sail suppliers, including sailsetc.com stock Dacron for this purpose. It does not stretch. I would use 25kg breaking strain for the running rigging. I also use 50kg or stronger for the standing rigging.
Dacron also runs nicely through fairleads, blocks and deadeyes, and ties off well.
I have used the teflon fairleads which work well, however they are not the correct color (white) and they don't look right. I use them for ease as they work well and are easy to fit however.
Dacron can also be coloured with boot polish and holds the colour brown OKish, but it fades to pink after a season or two.
Dacron takes black well for standing rigging and this does not fade anywhere near as much. A lighter coat of black on running rigging will show up grey, the colour of sun bleached rope.
As for minimum working radius. Really no, as long as the diameter of the pipe allows the rigging to run through freely. Really as long as the line will go through the angle without kinking due to stiffness. The biggest disadvantage with running over edges is wear. The problems with too long a pipe are threading/feeding the rigging through, and space below deck.
My two cents.