The de-joisting is continuing apace, and we’ve come up with a design to give the stairs some more headroom, a place to put a light to illuminate the stairs, and a way to deal with the re-joisting. Along the way, we’ve found that some of the removed joists have the weight of balsa wood, and one of them had been charred badly.
Charred joist – there were electric cables going through that joist 
Putting in the cross-brace for the new joists 
Opened up above the stairwell