imovie 08 question

[axeldtf]

I just imported a video to imovie 08, the video size was 1280x720. After doing some editing, adding text and some transitions, i went to share it to media browser. It only gives me a large option for 960x540. When i burn this on dvd it seems to be cropped a little. I am extremely new at video editing, however i was wondering if i upgraded to imovie 09 or final cut, would i be able to keep the aspect ratio, or is there something i'm doing wrong in imove 08, any help would be greatly appreciated. Thanks!