I have a large project that I want to make a dmg file of, but I get this message prior to creating the image: "If you use a disc burning utility to burn a double-layer disc image, the DVD may not play well in some DVD players. For best results, use iDVD to burn double-layer projects directly to a DVD." However, I don't know how to burn a dual-layer DVD in iDVD from a dmg file. Having searched around, I don't think it can be done. I have other dmg files and cannot import or open them into iDVD (unsupported format). So, how can I save my large dual-layer project to my external drive and be able to make a DVD copy in the future?