A point of clarity that took some time to sink in.
If you are trying to setup a group larger than seventeen, you are going to need to break the fellowship multiple times.
The first "break" has been covered thoroughly.
In the original notes, around steps 4/5/6, some clarity may help:
One your fellow has grown to ten, and you drop so there are three, consider the second and third group members *temporary* members while you are extending the group from two sub fellows to more. (Let's call these sub-group leaders A and B).
Have the two perform invites; get the group size to eight.
The leader will see much more than the temporary group leads.
Once the next split takes place, the new TWO stay (C, D and E, F). The sub-group lead does NOT stay in the fellow. This is NOT a pyramid structure. You are replacing one person who can invite seven with two. So when A creates a broken fellow with C and D, you drop members of A's fellowship, INCLUDING A - and do NOT drop C and D. Similarly in B's fellowship, you can invite seven (in this case with a leader, C,D, and B can all invite 7, this is a group size of 25.
And you can have B, C or D invite seven, "bust" it again. Once they do, KEEP the two who entered simultaneously and DROP B, C or D (whichever one was hosting the new group).
A pyramid came to mind as I started to learn this -- don't go there visually or mentally. You are creating a flat group of broken invitors under your original leader. Each can see the leader. If they see a parent/grandparent, they can invite fewer participants.
You are creating a flat structure under a single leader. Once a "broken" member is created, note they happen in pairs. The temporary, hosting leader of the group in which this new pair was created - needs to go.
Then everyone under the original leader can +invite 7.
And you WILL have disconnects and performance issues over 20 to 25 people. Stagger your portal entries and exits, and don't summon 20+ pets at once, and of course, your mileage may vary.