The shoulder hubs were assembled and glued today and detail pieces that go on the horseshoes were applied. And one of the mysteries of the universe was revealed when I dropped the shoulder hub into the indentation on the leg and slid the horseshoe into place. For the last year or so I wondered how to attach the hub to the shoulder. It was so simple ... The horseshoe holds it in place !
And another lightbulb turned on when I re-mounted the legs to the frame. Now I understand why it's not good to attach the booster covers with long screws from the outside of the leg. Because you really should have the boosters off to get an allen wrench on the one leg/frame bolt that's under the boosters. I'm sure I'll be able to tighten it using another method but it will complicate things slightly.
Progress on R2 is going a lot faster than expected.