Aspect Ratio Export Problems - HD Sequence

Hi All,

Have a problem that's been driving me nuts for a few days now.

I have an HD Project using FCP 5.1.2 and QT 7.1.3 with footage from an HVX200 shooting 720/24p and pn (one slow mo shot in the project).

The sequence settings are:
Aspect Ratio: HD 960x720
Timebase 23.98
Quicktime Video Settings: HDV 720p24

I'm not quite sure why the QT Video setting are on HDV, but when I set it to HD DVCPRO, the images is incorrectly displayed (get a green bar over the bottom, and it's stretched).

Here's the part I really need help with - when I export this as Quicktime movie, the aspect ratio is correct and it outputs a movie that is 1280 x 720.

When I export as SD, and I've tried with 11 different compressors, the image is squeezed into 4x3 if I leave "preserve aspect ratio" unchecked, and IT STRETCHES the image too much (to about 2:35:1) if I ask it to preserve aspect ratio using letterbox.

It's driving me nuts and I cannot get a properly sized 4x3; 1.78 letterboxed SD movie output to save my life.

Any help, greatly appreciated!