is there anything other than a faulty throw bearing that would cause clutch shudder in reverse only?

Dodgy pressure plate or maybe even gearbox mounts.

cable adjustment????

oil on the clutch

check the bowden tube has enough sag. its the black conduit underneath the car that comes from the chassis to the tranny that the cable runs through. It should have about 1"-2" of sag in it.

I'd say mountings. Bowden tube problems usually only show symptoms when going forwards under power. Shockies are also another big cause of axle hop in reverse, which can feel like clutch shudder...