Note on [27-28]: originally 2 PdB. modified by Drewry to SkCh. O. Otto says best variant is corners in PdB, 1c in SkCh
Note: on  the original says »RH«, but »BH« is widely used.
On 2nd chord 3c+4c cross to (1,2,3x,4x)
Note that both times the couple moving UP makes the arch.