I'm not sure if I exactly understand the question. I was involved one PTO with a large board that conducted all PTO business. Seemed odd to me at first, but I quickly learned it was a very good approach.
The general PTO had only two meetings, one in Fall to approve the budget and one in Spring to elect officers. Any member could vote in a general election.
The Executive Board, consisting of 5 elected officers, all committee chairs, 4 school officials, and a parent rep from each grade could be 25-30 people depending on how many co-chairs and committees were active. That group met monthly to transact any business and make all decisions. The meeting was open to anyone who wanted to attend, but only board members could vote.
We never really ran into the one vote per person or one vote per position (if co-chairs) that could be a bit sticky in a close vote of a small group. Frankly, most issues were handled during discussions and it wasn't too common we even had a vote that wasn't unanimous. But with that big a group, there was always a very clear majority anyway.
One other note on this type of environment. We tried very hard to be open and have good communication. We had monthly newsletters to keep members informed, we called the Board meetings "Business" meetings to make them sound less intimidating, and we advertised they were open to anyone who wanted to attend (observe).
If that doesn't tell you what you need, let me know.
Joy, I know you've written in these pages in the past about your unique structure which includes an unusually large executive board.
Can you (or anyone else) provide a bit more detail on how that works bylaws-wise?
Example: traditional = executive board meetings (exec bd members attend and vote) and general meetings (all members attend and vote). And EB is defined in bylaws. But if EB is more open, then how do you define who can vote at EB meetings, etc.