Manta:
Another option is the LowePro Vertex 300 AW. It also (barely) meets current US carryon requirements - but likely violates it if you pack it to the brim, including laptop. I can get my Ike housing, arm segments and clamps, strobes, all chargers and batteries, 2 bodies, lenses, and 6" dome port into it. The 8" dome port assembly (with neoprene cover and wrapped in a wetsuit for doublepadding) and the tray/handle go in the checked bag with the scuba gear.
I only suggest the Vertex as an option because it can be had about US$100 cheaper than the Think Tank stuff (which is no doubt excellent!).
