I have 2 projects I am trying to put on a DVD with no menu. They are 1.15 GB each and I have an 8.5 GB DVD. I set the project DVD size to 8.5 GB in the program. When I put them on the DVD, it says they are too big (It tells me they are 5 GB each).
That's because you are not putting compliant MPEG-2 in DVD Architect, so it is reporting the unpacked size.
Render your video in Vegas using the appropriate DVD Architect template.
Render your audio in Vegas using the appropriate Dolby Digital AC3 template.
Bring the video into DVDA. The audio will follow.
You have custom bitrate settings in Vegas to tweak the file size.
There are calculators to help you with this task. http://www.videohelp.com/calc.htm
This probably gets asked 2-3 times a week, even though it is covered in your interactive tutorials and help section.