Each person has a range of conversational contributions that they may feel comfortable with. A good university lecturer, radio show host, or stand-up comedian, for instance, might be able to sustain a maximum of 1.0 all alone for hours at a time. Someone with an inflated ego might not feel comfortable dipping below 0.5 for any length of time, whereas an introvert might range between 0.0 (pure listener) and a peak value they cannot sustain for long outside of a narrow range of topics.
So establishing the most efficient number of conversations, and their participants, becomes a form of the backpack problem. A conversation group can only achieve its highest efficiency of some people aim to fulfill different roles. Some participants are bulky and heavy, some are spongy and flexible, and others are small and light.
There's the baseline talker. This is likely the person with the highest sustainable coefficient. They drive the conversation. Then there are responders, who need to have a wide, tunable range of coefficient. They top off the conversation to 1.0 by adjusting their output to an appropriate value. There may be interjectors, who pipe up with a witty quip or relevant factoid every now and then, aiming for high return on low coefficient. There may also be swappers, who participate at a low level in multiple conversations, flipping to whichever one seems to have a lower coefficient, but less able to sustain higher coefficients than a responder. Sometimes there is even a gestural participant, who mainly contributes to the conversation with non-competing visuals rather than interruptable speech.
So having a single conversation with more than six people is easy. You kick out the baseline talker, get two responders to drive the conversation instead, and fill up the rest of the group with interjectors. This happens all the time in tabletop gaming groups, where the game itself adds a baseline coefficient, and the typical participant has a low maximum sustainable coefficient. Some people just don't want to talk much, and the game can create a structured conversation that pulls lower-coefficient players up enough to make the group reach 1.0 .