i just finished a project in dvda and the project took up 153% and dvda would not burn it. so i prepared the dvd through dvda and used DVD Shrink to compress it and it works fine. DVDshrink is a free program that can be download from the net
You definitely want to follow Spot's advice. DVD Shrink is great for getting yourself out of a jam, especially when a re-render and prepare is going to take ten hours and you have to deliver right away. However, you are much better off using a bitrate calculator (if you encode in Vegas), or use the shrink to fit option (if you encode in DVDA).
Here's a link to a bitrate calculator that will give you the bitrate that will make a single MPEG file just fit a 4.7 GB DVD: