We're back, and although I haven't had a chance to go through the results yet (349GB; ~15,000 images), my kit worked really well. The 200-400 was awesome, the 70-200/4 and Z15 "took turns" on my second 1Dx, and the 24-70/2.8 was handy on my "ancient" 1D3. My vest/belt worked great, keeping the BlackRapid double in place and putting things where I wanted them. The lens case was on my left side, since I kept the second 1Dx with either Z15 or 70-200 on the right side (the Z15 is manual focus, so by being right-side it wasn't strangling me with the strap while I put two hands on it, and the 70-200 was my secondary bear/whale/eagle lens so it could be handled single-handedly if needed). I had a utility pouch on the right with CPLs, memory card wallet, and spare camera batteries which I never needed though it did come close.

Maybe next time will be a 100-400II and a 600/4 with 1.4x...