Our method is to communicate concisely, up front, and often. People need to know what to expect... what will happen if a room is not full, what will happen if a room is full, what will happen if a room is full and only 2/3 of your group can attend. Will content be recorded and available fully later? Will content be recorded and available for a limited time later? Will there be access to session materials before or after for people who can/can not make it into the room?
We also feel it's best to speak to our most vigorous attendees about their needs. If we can get closer to offering what will be most attended, then we will have plenty of space. It's not a perfect system by any means, but if you're giving people what they need and want from your event, then you are one step closer to each session room being close to or right at capacity.We have also expanded capacity by tasking specific session facilitators, support staff, and others who can make super-user type changes on the fly in Cvent. If capacity can max out at 85, then we can set initial capacity at 70 & open more space as needed on the day of the event. The communication seems to be the best way for registrants and attendees to understand what to do, what to expect, and how important it is to be open about their needs so we can support and serve them.