My 200-400 is 8.25x4.75x4 and fits nicely standing vertically in the smaller bag.
Just to point out again, my bag is an Atan, but its dimensions are identical to the Domke F2 bag. Now that I have been thinking about it, I don't remember how the design moved from company to company. There may even have been a patent dispute for all I know. What I am certain of is I was aware of the Atan first, and they eventually went out of business and somewhere around there Domke showed up with the same bag using tougher material. The Atan is polyester and the Domke is canvas. Anyway, like I said, there is probably do disadvantage to getting the F1X instead of the F2. Photojournalists have been using those bags for decades.
Just to point out again, my bag is an Atan, but its dimensions are identical to the Domke F2 bag. Now that I have been thinking about it, I don't remember how the design moved from company to company. There may even have been a patent dispute for all I know. What I am certain of is I was aware of the Atan first, and they eventually went out of business and somewhere around there Domke showed up with the same bag using tougher material. The Atan is polyester and the Domke is canvas. Anyway, like I said, there is probably do disadvantage to getting the F1X instead of the F2. Photojournalists have been using those bags for decades.