I swapped the Canon foot on my 600 II for the RRS replacement foot, Arca-compatible and usable as a handle. I carry it on a Blackrapid left-handed sport strap (on the left side, so I can raise it and support the lens with my left hand, and operate the 1D X with my right), usually with my hand wrapped around the handle, but the BR strap bearing the weight.

I wear a Lowepro light utility belt, on which I carry a RRS MC-34 monopod with MH-02 Pro tilt head (held with a Maxpediton universal flashlight sheath). The belt also has a lens case 1N which holds both the 1.4x and 2x TCs, a lens case 8x6 which holds extension tubes (both 12 and 25 will fit, at the same time), and an S&F bottle pouch with a water bottle.