What version of Vegas are you using? If the pro version(s) you should have no issue going into custom and adjusting the bitrate for the file to fit more on the disc or to increase quality. You will want to use mpeg-2 and allow Vegas to do the conversion for you, not DVD Architect.
(choose the template for DVDA that fits your project- either widescreen or standard), then render your audio separately as an ac3 file.
You will need to download a bitrate calculator to get more exact settings for your DVD. You can find one here: Bitrate Calculator
j razz
https://www.jrazzcreations.com