Exporting a movie as an image sequence... cropped?

I've created a short sequence (4 seconds) in iMovie '09 that I am trying to export as an image sequence for insertion into a stop motion animation I'm creating with QuickTime Pro. The movie segment has been created with an aspect ration of 3:2 from TIFF images that are 1620 x 1080.

I can export the short sequence as an H.264 movie at the proper aspect ratio, but when I export as an image sequence, the individual frames are cropped on export to an aspect ration of 16:9. The images aren't stretched, they are cropped, and I can't figure out a way to get the QuickTime exporter in iMovie to export still images that are true to the dimensions and aspect ratio of the movie that appears in the iMovie project pane.

I'm not entirely sure, but it's as if iMove is picking up settings for the aspect ratio from previous project.

To workaround the problem I'm expoting an H.264 movie from iMovie, opening this movie in QuickTime Pro, then exporting the individual frames as an image sequence of TIFF files at the desired dimensions and aspect ratio. Needless to say, the resulting frames are losing considerable image quality passing through each of these steps. The sorry-can't-use-em cropped frames directly from iMove are adequately clear, but with the added step of making (and compressing) a movie, then exporting the frames from QT the image quality suffers.

As an aside, you'd think I could just paste the movie exported from iMovie into my animation sequence in QuickTime Pro, but I get a video glitch at the point that the iMovie originated sequence begins.

Any idea how to get iMove to not crop frames that have been imported at the same 2:3 aspect ratio as the project properties?

Thanks!

John