In the below video I do a comparison review between the CPM Cubed Cage 3 and the FilmCity Cage. There are two reasons you want a cage for your DSLR when shooting video. For one it protects your camera and lens while shooting. Secondly, it offers a place to mount multiple attachments such as a video light, microphone, field recorder, etc.
You can see below my 5Dmk3 in the CPM rig. It’s not quite level when holding the top handle. CPM does sell a small square quick release mounted sideways so you can move the camera side-to-side. It pops up and out though. I’m not sure the camera will clear the top plate since I have it mounted slightly low (so I can add 15mm clamps to the tops of the rods).