Most multiple ig housing goes bad within a week, and the vet bills and suffering build up. It is generally and rightly assumed that igs are strictly solitary animals, even though there are exceptions. They don't understand the term "lonely", even though some igs suffer when their keepers are away for a week or two. But they sure don't miss the company of other igs There are likely to be a few exceptions to all of this.
One was reported by a board member who witnessed a gathering of iguanas on the vines that were hanging down a well. We assume they enjoyed the cooler temperatures there. But what goes for wild ig does not necessarily work well for captive igs.