I've been using vegas pro for about 15 years (but still an amateur), mainly v13 but I also have v15. I'm running on i7-4770 3.4ghz on windows 8.1. I shoot in 1080 60i, and usually have great success when rendering for DVD using the standard settings for mpg2 customized for DVD architect rendering to ac3 audio and video widescreen. I've found that there is usually a limit at the standard render settings of about 1.5 hours when using a single layer DVD and 3 hours when using a dual layer. I have a project that is coming to me in 1080 mp4 shot in 24p. It's 4 files that total about 3.75 hours. at 1080 the mp4 files total about 6.8 gig (which seems like it would render down and still fit on a dual layer), but when I render to 480 mpg2, it suprisingly increases to 9 gig. My questions are: if I use the standard variable bit rate (that averages out at 6 Mbps) the size of the file increases? (as I render each of the 4 mp4 files to mpg, they change, for example, from 1.8 gig to 2.2 gig, even though I am going down (from1080 to 480). The only way I can get the file size smaller is to use 4.2Mbps). Is that my only choice to fit the 3.75 hours on a dual layer? Thanks so much.