Rules for 7-couple sets, generalized

I have been thinking for sometime that there shouldn't be any reason to not use the 7-couple rules for 10 or 13 couple sets in scottish country dancing. Generally, the formula is 4+3N, where N is a whole number > 0. This means that the rules can be used for 10, 13, 16, 19, 22, etc. couple sets.

In a 10 couple set, suppose the couples are numbered from 1 to 10.

1. In the first time through, couples 1, 4, 7 are dancing. couple 10 is idle.
2. Second time through, couples 2, 5, 8 are dancing. couple 1 is idle. Couple 2 borrows couple 4 for their dance (who would normally be idle in a 4 couple set). Couple 5 borrows couple 7 for their dance (who would also normally be idle).
3. At the end of the second time through, couple who end up in 9th place slip to the end. Couples who end up in 3rd and 6th place stay where they are.
4. Couples 1,2,3 stay in their little set and bollow couple 4 when needed. Couples 4,5,6 also stay in their own little set and borrow couple 7 when needed. Couples 7,8,9,10 dance according to normal 4 couple set rules, except with borrowing of the 7th couple by the previous set.

If there are 10 couples available, it may be better for one 10 couple set with above rules rather than 2 five-couple sets:

1. If playing music 5 times, the dance takes extra time especially for strathspeys.
2. If only playing music 4 times, the last 2 couples may get to dance only once through.
3. There will be lots of standing around in a 5 couple set, with attendant problems like cooling down muscles.
4. 2 couples are idle at any time in a 5 couple set (40% idle). In a 10 couple set, only 1 couple is idle (10% idle). In a 13 couple set also, only 1 couple is idle (7.7% idle). As the length of the set increases, the percentage of idle couples decreases.
5. Extra dancing within each  3 couple "little set" in a 10 couple set. Of course the flipside is that people get less rest.

13 couple sets could also be advantageous, because the alternatives to a 13 couple set are as follows:

1. 2x 4 couple sets, and 1x 5 couple set. Again, there are various combinations of the above problems.
2. 3x 4 couple sets, and 1 couple don't dance.