720p sync

I'm having an issue with sync. I have footage shot at both 1920x1080 and 1280x720. I have FCP 7. The footage is from a Sony F3 so it is XDCAM. I have edited a sequence in both XDCAM and ProRes at 1920x1080 and everything is fine when it plays back, the sync is right on in the external monitor.

However, when I edit the same footage in a timeline that is 1280x720 my monitor is WAY out of sync. I want to edit at 1280x720 since MOST of the footage in the spot was shot at 720. Also the only shot at 1080 I want to scale up and zoom in a bit, so I figured editing in a 720 timeline will give me more latitude. The audio for the spot is coming from the footage shot at 1080, the video from the footage shot was at 720 in overcrank. Only one scene has both the audio and video that was shot at 1080, and by the time that scene plays it is out of sync in the 720 timeline.

I have tried many things to fix this sync issue. I have an AJA KONA LH control panel, which is set at a 720p format, same as the output on my FCP control panel. I have tried switching to different setting on both and have not gotten the 720 timeline to go in sync.