mount disk image on boot?

I would like to mount a disk image at boot as if it were a "real" disk.

My first inclination would be to add a "hdiutil mount diskimage.dmg" to rc.local, but I want to ensure the disk image gets mounted before the application whos output I intend to jail launches.

Any ideas? Would this be possible via fstab?

I’m running 10.3.9 server (though this would come in handy for my desktop too (10.4) now that I think of it.

Thanks,
Mike