In a recent tip we suggested that you manage the expectations of your exhibitors. Here is more on this.
First, why publish a promise of 10,000 attendees in your exhibitor prospectus when you know that only 6000 will show up? Better to promise 5000—then the 6000 will make you look good (under promise and over perform).
Also, gladly accept the responsibility for helping each exhibitor have a good show. For example, say that a 10x10 exhibitor decides to step up and take a 20x20. The proactive show manager: