it's been a while, but I think I had my flash guy export sequential stills in the correct aspect and video frame rate and with enough safe area. I think flash by default is 12 fps which will make your video really fast. That was about 2 years ago, the new version of flash probably has setting already.
one thing i did the other day was to use Snapz ($60US) screen capture software. screen res set for 1280x854; captured a streaming video file with a bounding box at the default of the movie 320x240; capture rate of 30fps; internal sound. brought the file to m100 keeping the aspect; the file was a bit larger than 1/2 screen and (for streaming video) looked amazing! Partly i'm sure because of fewer colors of NTSC.