I can't tell there, but do you use the tripod collar and mount the SB or is the camera mounted normally? Do you use a rail lens support? How comfortable are you walking around and holding it like a normal DSLR and lens without any attached gear?
It's mounted to the tripod plate via the SB tripod foot to take pressure off the camera mount. For quick guerrilla grab shots, I attach an R-strap to the GH4 and shoot handheld without any gear, just with the Rode mic. I don't use the follow focus you see here, it's only for show.
I balance and focus the camera with my left hand under the Sigma and my left elbow braced against my front body. My right hand support the camera on the handgrip. This works well for me when I need to move fast. The weight of the camera with the Sigma attached feels like a much larger camera. When not at eye level, I can comfortably carry the whole thing in one hand, which I do at the aperture ring to distribute the weight evenly. I let it hang on the strap if I need to free my hand momentarily.
For extended handheld shooting, e.g. events, I use the Zacuto DSLR Recoil, the best designed rig ever for small DSLRs.
