Not sure if this is the best way , but the way I do it. 1st-render final 2.5 hour wedding clip to one file same as you shot it. Ex. if you shot 24pa render as 24p 2332 pulldown. 2-bring that file into dvda and do whatever you normally do. 3-when burning click the button called optimize and then fit to disk. This will take the roughly 30 gig file and squeeze it onto the 4.7 gig dvd. I just did one with about a 30 GB file andf 2 hours and 25 minutes of footage and it took about 5 hours to render another 20 minutes to burn. (render it before bed)
My other method—You can render in vegas to the preset dvda file and do the ac3 thing but when you bring it DVDA it will not fit on the disk and you can’t get it to optimize or fit to disk. I tried for 2 hours once.
Hope this helps or some one give a better way to do this.