Natively, a Canon C300 will not play nice with the Angenieux Optimo DP Rouge zoom lenses, but with a bit of sanding and a replacement part the two become a match made in heaven.
Because of the length of the Angenieux's back element it will not properly sit in the Canon C300 PL mount, but with a little elbow grease the space is made and the lens is happy.
In the above photo you can see the markings above and below the sensor that allow for the extra room for the Angenieux's rear element. Not only is that part of the camera modified, but the piece below the sensor is also swapped out for a piece that creates even more room within the camera.
This image shows how little of a change is necessary for the lens to fit, but without that extra space you'd be out of luck!