We have a V. It's effectively an open V in that we will allow for the possibility of other partners. Functionally it's closed-because none of us HAVE other partners
(Maca DID have a one night stand with a close friend as noted in another thread about it in order to decide if he COULD even handle abeing poly but that's not a story for THIS thread).
Our rule is that in order to take on another partner-we all have to agree. Also we have a rule that none of us is allowed more than two partners-which means I won't be taking any more as I'm already sexually involved with both of my men. They are both straight and are each able to have one more woman.
What we WANT is ONE more woman to create a CLOSED poly-quad. So both men would share both women, and if that woman was bi (as am I) then we may share one another as well. But no one else involved sexually.
I don't think it's necessary to have a poly relationship that is open to ANYONE. I think you have to identify YOUR desires and what you can handle then aim for that.
For example-we agreed to the one night stand as a one time thing for a speciffic purpose and we all agreed on who she would be (a close friend we all trust). But as a rule-we don't allow for one night stands or FB's. We're pretty strict between us about safety, sexual, physical, emotional etc.
We're a family with 4 kids. We don't have room for a bunch of b.s. in our lives.
"Love As Thou Wilt"