Optimum AVI size for PAL 16:9 DVD?

I can choose the size when screen capturing my original AVI clips with
FRAPS. And I can ensure that they give the required aspect ratio of
16:9 for use in making a DVD for PAL widescreen TV. For example I can
make the AVI:

1888 x 1022
1504 x 816
992 x 558
etc

But am I right that any height over 576 would be wasted, given that
the DVD-ready MPEG output from any editor will be 720 x 576?

If so, and I choose 576 as my height, is the optimum size 1024 x 576?
Is it correct that anything larger than that won't improve the final
quality of the DVD at all?

--
Terry, East Grinstead, UK
.