Rear end done.

Here is the finished rear frame viewed from behind. Admittedly the rear "loop" is a bit over engineered, since its only purpose in life is to prop up the upper part of the carbon fiber seat unit (and provide a bit of torsional rigidity to the rear frame). But I wanted it to look sturdy, in order to impress the M.O.T man, with whom I have a date in a couple of weeks. At first I had planned to cut off the two protruding pieces of tube (left and right lower corner), but they do a good job of supporting the rear part of the rather flimsy seat unit, so I think I'll keep them as they are. They won't be visible when the seat unit is in place anyway.