If you're shooting with a Canon C300, and you really like the traditional 35mm handheld Panavision look, the Shoulder Cam Bundle for Canon C300 Camera (With EVF Mount) from Letus35 may be just what you seek. This rig was designed for shoulder-mounted camera work, and it mirrors the feel of a real 35mm film set-up. You can mount a full C300 system while you keep the weight centered on your shoulder, like Hollywood pros have been doing for the last 40 or 50 years.
Using an (optional) EVF on the included adjustable EVF knuckle makes it possible for the rig to be very compact. The rig easily breaks down into smaller parts so you can go quickly from handheld to tripod and back--the release system is so easy to use, you can lock and release them one-handed, even in the dark. This is a system that closely matches the feel of a true Hollywood camera.