Hei Adam,
When you import your footage to FC (FC dosn’t knows it’s 16×9), in the brownser you must check it as 16×9. You do it in the column “Annamorphic’. Then you can drag it to a 16×9 sequence, where you will get a full 16×9 screen, or to a4x3 sequence, where you will get a 16×9 image on top of the 4×3 screen (same if you would crop a 4×3 image).
Then when you export with Compressor you have to specify the kind of MPG2 (16×9 or 4×3), depending of the option you have choosen when setting your sequence in FC.
The only problem of making a 16×9 DVD, is that some old DVD players can not read them as 16×9, so the film is displayed as 4×3 (deformmed). If you use the second option, everybody will see a 16×9 image, although been 4×3.
I hope you can understand my English, and this can hepls you.
Salud,
Rafael