There's an application called PatchBurn that adds support for unsupported drives. Do a google seach for it. Of course, "use at your own risk". I must say, however, that the Sony burner you mentioned is very likely to be natively supported in Tiger. What OS version are you using?
If you want to use Toast, select "hard drive" and "IMG" in DVD Studio Pro's format dialog (instead of choosing the internal drive) to export an encapsulated image file of the DVD. Then, in Toast, you choose "copy" (instead of data or video) as the main option, and "image file", in the options. That will allow you to burn the image file to a DVD, with all mastering settings from DVD SP. There are other ways of doing it, with the VIDEO_TS folder itself, but those other ways change a bit depending on which exact version of Toast you use, and sometimes they require that you manually delete some DVD SP layout files.
Adolfo Rozenfeld
Buenos Aires - Argentina
www.adolforozenfeld.com