LR, I don't get a load of time to read a lot of the blogs, but given the recent discussions we've been having on various threads, I thought I would dip into here.
I have a suggestion - sort of a way of thinking and the actions that may come out of that. Not sure whether it will fit with your dynamic, but I thought I would put it out there....
Each time someone new comes into the constellation that you have, the dynamics are going to change - you have different personalities involved. Each person has their own set of needs, wants, likes and boundaries. Trying to make your currently negotiated set fit with this new person may be a real challenge. Pressure is then put on people to "ignore" certain things, and the games begin.
You have a 3 month timeframe to do a review of your negotiations - to see what still applies, where the pressure points are, and work out as a group what needs to be changed, yes? Maybe that should be reset when someone one new joins. Schedule your usual type of meeting, but with the new person - everyone gets out on the table what they need out of this, and what their boundaries are - everything is first-hand and folks get a chance to have a clarifying discussion about any potential places of dissonance.
If the are conflicting needs and boundaries and no solution can be found, then really there's not a lot of hope for it working, because those will ALWAYS nag at you. If you can reach an agreement then the pressure will be off because everyone will be going into it knowing their needs and concerns have been heard.
You then reset the 3 months clock to start at that point in time.
Anyway, just a thought....
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