I posted on cloudy nights as well but I'm not seeing this slow behavior with USB. Image download time is around 7 seconds with defaults. The only way I can get it slower is to use FITS + RAW and that's about 12 seconds total. Which isn't too surprising as we have to convert and write out an additional file.
But if you're using defaults then you should just be getting a single FITS image. You can check to see what file type you're using under the settings for the Canon camera.
Thanks,
Jared