Some events are being restrictive on camera bags (and other types as well). For example one military air show will only allow clear bags.
The LA Auto Show restricts bags to no larger than 12x15x6 inches in size.
I will be attending the auto show with my Canon 6D and 24-70 carried on a Black Rapid (no case).
I'll also take my Canon 70-200 f2.8 II, so I'll need a bag for it that conforms to the auto show policy.
With the hood reversed, the lens measures about 9" long by 4" wide.