2GB sure is a lot of loss/compression. I noticed your title is dual layer; so why not use just 1 quality DL DVD (DVD9)? They are 7.9GB instead of that 4.38GB DVD5.
(1024 megabytes = 1 gigabyte, not the 1000 megabytes marketers use / "Japanese gigabytes")
DVD5 a one-sided single-layer disc that can contain up to 4.38 gigabytes.
DVD9 a single-sided dual-layer disc that can hold approximately 7.95 gigabytes.
DVD10 a two-sided DVD5-type disc that hold single data layer on both sides; it can contain up to 8.75 gigabytes of data, with 4.38 gigabytes on each side.
DVD18 a two-sided DVD9-type disc with two layers of data on both sides of the disc; it can contain up to 15.9 gigabytes of data on it, with 7.95 gigabytes on each side.