Anyone use toast to burn DVDs?

[Hal]

I'm trying to burn a DVD of about 2 hours of video. When I set it up in 
Toast, it tells me that I need 5.6GB of space to burn it, and the blank 
DVD-R only has 4.4GB. Has anyone used the more expensive double sided 
(9.2GB) DVD blanks on a Mac? I'm using a Pioneer mechanism (DVR-105, 
LaCie external firewire drive). I have Toast 6, and imported the DV 
files into iMovie via a firewire bridge.

Any help is appreciated.

-Hal