We've been making steady progress with our daughter Dorothy, and we recently reached the point of practising touches of Bob Minor in which she was unaffected. She has taken to the 3-4 pair in preference to 5-6, so instead of calling three homes with her on the tenors, we tried singles that leave 3-4 unaffected.
The most obvious touch is two singles at wrong, swapping 2 and 5 while 3 makes 2nds.
Another touch is two singles swapping 2 and 6, which are when 4 makes 2nds.
This takes us in the direction of the kind of compositions I like for surprise royal and maximus, with 3-4 remaining in the 3-4 position. Calling singles every time 3 or 4 makes 2nds gives 180:
180 Plain Bob Minor 1 4 23456 ----------- s s 63425 s s 53462 s s 23456 -----------
Every course is 5 leads as usual. In total there are 6 courses available with 3-4 unaffected. The 180 visits all of these courses but doesn't ring the whole of every course. To do that, we need to omit a single somewhere and repeat the whole calling. Just for fun, here it is with 123465 as the half-way row:
360 Plain Bob Minor 1 4 23456 ----------- s s 63425 s s 53462 s 23465 ----------- 2 part.
Can this structure be extended to a 720? We need to add 3 courses with 3-4 coursing, in each part. Inserting a block of 3 bobs at the end gets close (these are homes from the point of view of the tenors, but remember that 5-6 are swapped at this point):
600 Plain Bob Minor 1 4 5 23456 -------------- s s 63425 s s 53462 s 3 23465 -------------- 2 part.
How to get the missing course in? A single at the second lead, from the plain course, changes the coursing order from 53246 to 56243 (swapping 3 and 6) and puts 3-4 coursing. So we can insert a pair of singles at 2:
720 Plain Bob Minor 1 2 4 5 23456 ----------------- s s 63425 s s 53462 ss s 3 23465 ----------------- 2 part.
and there it is, an extent with a regular structure for 3-4.
To enter this kind of composition (based on numbered calling positions rather than positions of an observation bell) into CompLib, you can use a : to show the end of each course:
1 2 4 5 s s : s s : s : s -: -: -: