I'm waiting to see what Jon recommends. I'm guessing, a Domke F2 with a different insert? I don't think that the F3X is large enough to carry that lens mounted on a camera. Bags are a delight to work out of, when you get the size right. Consider adding the Domke Postal Pad to the strap. I'm glad I did.
Think Tank Retro. Think Tank makes beautiful bags, and they're great quality. I suspect that a TT Retro 20 will do a better job with the 70-200/2.8 mounted, hood reversed. It's a deeper bag. An alternative would be a Retro 30 with the camera in horizontally...I don't think the Retro 10 is a deep enough bag to carry that lens mounted on a camera body. I can't check because I don't have your gear. I know that you want the smallest bag possible. Just wouldn't be my choice.
LowePro has just announced that the Classified series is discontinued. You may find the right bag at the right price! The Stealth Reporter bags are great too.
Lately I've been buying bags on the small side. We have had small cars for a long time. Problem is I run out of space; also, working out of a full bag allows some of them to collapse when you remove camera or lens. Then it's hard to get the camera back in.
I still have 4 Think Tank bags, and a bunch of LowePro and Domke. I'm not trying to catch up to Jon.