Dual layer disks do not have to be flipped to burn to both sides. Those types are called DVD-10, sometimes known as “flippers”, and are hard to find anymore.
Dual layer disks are called DVD-9 and have two recording layers on one side of the disk. The basics can be seen in this Wikipedia entry: http://en.wikipedia.org/wiki/Dvd
The vast majority of commercial dvds will fit onto a dual layer recordable disk, so compression isn’t necessary. The problems with dual layer are cost, lack of good choices and sometimes you might run into compatibility issues. The only dual layer disks that are recommended around here are made by Mitsubishi and sold under the Verbatim brand. And of those, the ones made in Singapore are the more consistent.
If you have an older burner capable of burning DL, get the +R 2.4-4x speed Verbatims with the mid code MKM001. If you have a newer drive, you can use either the slower MKM001 or the MKM003 which are 4-8x I believe. I’d burn them at 4x personally, since they are expensive, even on sale.
Compatibility problems might show up on older players. I haven’t run into this myself, but I know it does happen. You’d have to test this for yourself on your dvd player.
