I use a Canon grip on my 7D. It's the only way I can grasp the camera with all my fingers. Otherwise, my right pinky is left underneath it, and that is uncomfortable.
I typically use the Gripped 7D with a 100-400L, and when I handhold that, my right hand is on the camera and grip, and my left hand is under the lens, supporting the majority of the weight. Same thing if I get out the 430EXII and Better Beamer.
Your right hand should be bearing very little of the rig's weight. Your left hand should be holding it all up, either from the bottom of a longer lens, or with the palm supporting the base of the camera/grip, and fingers on the lens.
Oh, if the tripod collar foot is too small or uncomfortable, get a mount plate like an Arca-Swiss style. I have a Wimberley P20 on my 100-400 and it makes holding it a lot more comfortable.