I can understand where you're coming from about wanting a smaller file to see if it's worth comitting to downloading a DVD version. I have been thinking lately that MP4's might be a good way to go. Instead of Xvid there could be an MP4 version (which would be around the same size as an Xvid or less) and then two criteria would be fulfilled:
1. There is a smaller version of an edit to sample before trying to get a DVD-R version
2. That smaller version would be in iPod/PSP format and would allow people to watch the video on the go.
Is that such a bad idea? I think a few of OCP's projects have versions like this ("Return of the Ewok" and "The Thief and the Cobbler: Recobbled Cut" spring to mind).