3c+4c begin on opposite side (1,2,3x,4x)
5c (dancing couple) stands facing 1c in centre of square set, numbered clw as usual.
after 5 times through, 5c finish in the middle, all other C have moved one place clw
3c+4c cross on 2nd chord(1,2,3x,4x). This dance has top/bottom symmetry
Note: [27-28] was originally 2 PdB in promhold.