5,040 Stedman Caters

Donald F Morrison (no. 999)
231456789  6 12 13
412356987    (a)
1423             s
142356897     s
4123       s      
Repeat eleven times.
(a) =  2.s4.5.10.s12 (16 sixes)

If it is preferred to have the 6 in 5ths throughout, start at backstroke from rounds as the first row of a slow six, coming round at handstroke. Note that with this start the first bob comes at the first six end after the start.