I am using FCP 7, and as far as I know it does not read Canon C300 files natively. I tried Canon XF utility, with very limited success, on few different machines. Main problem with that piece of software is that it expects to see compact flash cards straight from the camera and doesn’t seem to work very well with folders on an HDD. I was suggested to convert MXF clips to Apple ProRes 422 using UFU Soft MXF Converter for Mac, because FCP 7 needs to have all the footage on a timeline in the single codec, otherwise it needs to render everything and does not preview clips in realtime. The Canon Video Converter tool is able to load MXF files directly from the camera, or read from a folder stored on your computer’s HDD or an external hard drive, as well as separate .MXF clips out of the camera’s original folder structure. Plus, this solution is particular helpful when you need combine footage coming from different cameras with different video modes. Best of all, it is capable of keeping multiple audio tracks in your source material.