So I've been using the Wimberley WH200 gimbal head and enjoying its use, if not its weight. I also wanted to be able to quickly transition to vertical positioning of the camera. I know the Mongoose 3.6 is a popular option, but I picked up the Wimberley CK-100 sidemount conversion kit and it worked extremely well for me this weekend. Rig is smaller, lighter and a breeze to rotate the camera. Admittedly, only shot with the 100-400 II on it, still yet to try longer lenses. I do think it will pack smaller for travel. Here is a shot of the US Navy Blue Angels taken with the set up, 5DIV body.
Name:  36606055193_e5bfe6b281_b.jpg
Views: 176
Size:  145.6 KB