[X4U] Copying a 5.3 gig DVD image?

[Jeff Porten]

I have a client who wants to burn a backup of his iBook G4 install  
DVD -- but it mounts with a file size of 5.3 gigs.  We tried to use  
hdiutil to compress the image we made of the disk, but it's still  
over 5 gigs.

Any ideas?  This is a normal, everyday DVD, no dual-layer or BluRay  
or anything like that.

Thanks,
Jeff