I've got a similar set up that sports the C10 SIRUI head, which was indeed a little small for the job. It did manage though. It was on a set of flyweight induro legs. It came with me to the top of Machu picchu
K10 would indeed have been a better choice.
Without a doubt this tripod/head combo can hold the 5D3 size body and/or even a 1d with any prime up to the 135L. You WILL have to use mirror lockup/remote trigger or 2 second timer just to get the thing to stabilize. It's not a rock solid hold your hand on the camera and shoot away. It does take proper technique.
For what I need, this thing will work great.