Crazy one:
I've just started using component video myself and, while researching the subject, must have read that thread at least three times but I just don't think there is any way you can fill the entire screen without either ddraw with hwstretch or D3D instead of ddraw.
The only way is if the video card scales the image before sending it to the screen. I have noticed that most video cards do this for S-video but for component, they simply enable panning and don't scale the picture. The result is that if you specify a resolution larger than 640x432, the screen will only show the portion of the picture that fits that pixel area.
This pretty much kills the D3D alternative because if you use D3D with 640x432 the resulting image is of very low quality and you will notice all sorts of stray pixels. With ddraw hwstretch, the image fills the entire screen and the pixels look correct but you induce some blur. I have found that increasing the sharpness control of the TV to the top quarter of its range compensates well for this (you should also decrease color and increase contrast to improve the image overall) but this is not, say "arcade perfect".
Overall, I think the result is very good but I wish there was a way to force the card to scale the image without hardware stretch.