Felgue,
In my experience, hirez images can contribute to a flickering problem in FCP. I am a firm believer in optimizing images in Photoshop, and this is the recipe:
Double-sized (as stated above) tiff files at 72 dpi. I have done several tests using this sized image at 72 dpi and 300 dpi, and flickering is much less of a problem in the former image.
Also, the flicker filter or a small amount of gaussian blur is usually all you need to get rid of the flicker entirely.
Have a wonderful day.