I regularly carry my 5d3 and 70200 2.8 ii on a black rapid strap (both the double and the spot version) with absolutely no problems or worrys.
I usually keep it attached to the tripod mount just so that it is more evenly balanced
ditto, I carry the 100-400L with the 5D3 (similar in size to your combo) with the RS-7 and jave absolutely no issues or worries. I leave it on the tripod mount at all times. Its just so much more comfortable with a 5+ lb setup on your shoulder as opposed to your neck like the canon strap.
+1 for the Black Rapid RS-7 and 100-400. It hangs by my hip right at my right hand and is evenly balanced.