The final parts arrived by mail from England today, a pair of Surly Large Marge inner tubes. It seems the tires and inner tubes currently are out of stock from the supplier, and only available in shops that happen to have them in store, a something which changes rapidly. I did try two different DH inner tubes instead of the Surly ones, but had no success.
Anyway, the build is done. The riding position will still need some adjustment and the gear cable has to be shortened, but otherwise it is ready.
8-speed Alfine .
A fixed hub with a sprocket in the front for backup, should the rear hub break down.
Surly Larry in the front.
Surly Endomorph in the back.
During the fall, it will get some bikepacking gear: A full sized frame bag, possibly a front rack and bottle cages on the fork and possibly under the down tube.