I purchased this because I like to have two cameras with my kit. One for up close to mid range, and one for telephoto capabilities. This gives me the flexibility to hike, and have both cameras at the ready.
This kit provides some safety harnesses, you MUST use these! The one complaint is the piece that screws into the tripod attachment, can work it's way loose. I had my 5D, with a 400mm Canon Prime Lens, and a 2x III extender on my hip location. The connector had worked it's way loose, and the camera fell like a rock...but was caught by the safety strap. I lost my breath for a moment, but it worked and my camera is safe!
I recommend this option, just be sure to screw in the connectors tightly, and use the safety straps!