Charlie, Edward has been at this a lot longer than I have so I’d listen to him 🙂
Since you asked though, for a 2 hr. DVD, my bitrate calculator says:
CBR: 4,576,000
VBR: 8,008/4,576,000/2,744,000
BTW, I’ve got it set to a 5% safety margin instead of the default 1% which is why my numbers are a bit lower than Edward’s.