Since there is still not enough space on a regular DVD+R DL disc to hold the entire XGD3 game partition, not to mention the Layer 1 Video partition, this is not at all recommended as being "safe" for Xbox LIVE.
XGD3 backups will still boot and play fine on LT+ v2.0 as long as the last approximately 1.7% of the game partition does not contain any of the actual game assets, which it usually won't because the end of the game partition is near the inner edge of the disc, and developers will try to keep their game data near the outer edge (middle of the game partition) to maximize read performance.
Another necessary condition to booting and playing XGD3 backups on regular DVD+R DL media is that the kernel or game code itself must not perform any CIV (Content Integrity Verification) checks on any part of this last approximately 1.7% of the game partition (or at least it must not take any action after CIV failures). Even if there are no actual game assets in this area, there is still pseudo-random padding data which can be checked through CIV, and such checks can even be added later to the game code through title updates, or to the kernel through system updates.
Read more:
http://www.ps3news.com/console-news/...#ixzz1dxK2RhET