{{explanation}}
3s & 4s start on opp sides

1-8
: 1s+2s also 3s+4s set, 1s+4s cast in one place as 2s & 3s cross up/down:
  all dance 1/2 double 1/2 Figs of 8 to end 2 (1) 4 (3)
9-16
: 1s+4s dance RH across & LH back
17-24
: 1L followed by 1M dance Tandem reel of 3 across with 2s (LSh to 2M) as
  4L followed by 4M dance Tandem reel of 3 across with 3s (LSh to 3M).
  End with 1s+4s facing corners 1L/2M, 1M/2L, 4L/3M & 4M/3L
25-32
: 1s+4s dance 'Hello-Goodbye' setting & end facing opposite corner
33-40
: 4s cross up between 2s & cast to end 2nd place own sides as 1s cross
  down between 3s & cast to end 3rd place opp sides; all 4 couples turn
  partner RH