Here, with an update here.
Wow! That's some scary stuff! It just goes to show you how what engineers might see as a very small design change can have unforseen consequences. I've been using the Arca B1 for years with the Sidekick, tripod slung over my shoulder with the 1DII and a 500mm lens protruding, with nary a second thought.
I almost sold the B1 because the Z1 is about 5 ounces lighter, but the B1 has served so well that I decided not to part with it. Now, it turns out that the Z1 could possibly have parted with my Sidekick, camera and lens had I traded up.
It makes me wonder about all of the glued joints in the hi-tech tripods and monopods, and whether I have to change my habit of walking with the stuff over my shoulder!