I forgot.  The piston each have fine ribs along the barrels, to keep them in place when inserted.  This is no good to me, because i) the holes have been drilled to be extremely tight, and ii) several of the pistons have writing on them, and need to be lined up exactly.  Rather than ribs, the pistons will be kept in place by a small screw driven into the barrel from above.  So I have spent the last couple of hours carefully shaving off the ribs of each piston.  My thumbs hurt.

Soldering next.