Everyone who knows me on cdf knows that I love CloneDVD. But this has always bothered me. While it's true that "ISO Image" is what it says on the button and in CloneDVD's manual but i submit that it is not a true ISO "image", but rather just a very large file that contains all the DVD files. But as far as mirroring the original, something has been altered. Perhaps this is an allowable use of the word "ISO Image", but people who backup dual layer assume that the word image is synonymous with the word "mirror" meaning an exact 1:1 mirror of the original that doesn't throw away the the original layer break in favor of it's own.
If you did create a real ISO Image or mirror of the original, then the layer break would be preserved. Like with CloneCD or DVD-D/ImgBurn. Since CloneDVD is a trancoder, it just doesn't do that by design. It is my understanding that a transcoder is the wrong software choice for making true 1:1 DL backups.
But CloneDVD does a very good job, nowadays, of creating a working layer break even though it is not the original layer break. So, I'd like to add that new posts by people using CloneDVD to make DL backups (with Vebatim +R DL media that has been booktyped) and having freezups at the break point is a surprise to me! I had relegated these problem posts to the past since even some testy, rude (in the past) users have reported having good player results now from CloneDVD's "automatic" layer break point.
Someone refine my opinion or phraseology if you would care to.