It was at 6.0.7 last I used Toast, and it had a DL option where you select CD or DVD. If you don’t see it there, chances are your version doesn’t support the DL burner, but it a free update.
What I have done if I want to go DL is build the DVD to a VIDEO_TS folder. Then I burn that huge single TS folder in Nero 6 Ultra Mega using their DL option. Toast should do it as well, so should Gear Mastering Edition. Gear will allow you to set your own layer-break. I have no clue how to set your own layer break in Nero or Toast, or if they will even honor your set break point. They just do their own thing as far as I can tell.
Sacci used Creator and made some DL disks with Toast I believe, perhaps he can shed some light on your Creator workflow. You can find Sacci as a forum leader in the DVD Studio Pro forum.