Probably easy answer - irritating export aspect shift...

Im having a irritating problem when trying to export my video.

I started with a widescreen video but set my sequence to 4:3 and pixel aspect to NTSC DV. I adjusted the sequence picture and expanded it so it was no longer widescreen and filled the viewer fully. It did however keep the same aspect ratio.

When I try to export the video in H264 - at 4:3 ratios - the screen aspect changes and my subjects end up looking slightly wider and squashed. Ive compared the .mov file in quicktime aligned up next to the viewer in Final cut of the video I exported - and the exported video is clearly slightly squashed in its aspect.

I tried both 'current settings' on export and a couple of 4:3. Also retain aspect ratio via 'crop' - and got the same result...

Any ideas?

Thanks