I have posted a couple times on this already. And as of right now there is no way to copy this at the moment. There are several people currently working on this right now. In the past there has been some speculations that the fix would have already been released but it has not as of yet. I am one that is looking forward to this fix.
At first people were assuming that the problem was with PTP/OTP but that sounds like that is not the problem but anyways Team Toxic is working on it. and my understanding is that they are very close
I have tried several times and wasted many disk. If you are to try to make a copy it will start but quickly fail. There has been other people that have reported makeing a back up of it but they have to use the original everytime they have to change a race or go into the garage...pretty much evertime the PS2 has to load something new....thus being useless of having a back up copy because you are using the original more then you would just by sticking it in and playing it.
Rest assured when I see something on it I will post it in the Console Forum under Standalone Device forum
Here is a quote from ps2hd.com and for more look at afterdawn.com
DVD9 games on DVD+r dl now playable, including GT4
- by Dv8 On Mar 14, 2005 - 6:00 AM
Up until now, it has been impossible to play DVD9 backups placed on dual-layer DVD+r media due to the different physical format of the data on the disc.. Pressed = PTP, DVD+r = OTP
However, "Team Toxic" has discovered a software hack which enables DVD9 games to load from DVD+r dl media.
This also means Gran Turismo 4 is also playable on DVD+r dl media for the first time, including all other DVD9 games.
The Toxic flash release for DMS4 coming up in the next few days will include DVD+r dl auto-patching to apply this software hack on the fly, making DMS4 the first modchip to fully support DVD+r dl media.
Following that will be a DVD+r dl image patcher which will apply the soft hack to any DVD9 image before you burn to dl, which will let you play the games using any modchip.. That's "Team Toxic's" gift to the scene.