Bootable backup over the network?

[awm]

Dave,

thank you for your reply.
However, some bits of the "Airport Disks" article leave me a bit confused, even after looking into the SD manual.

Especially this:
"I'd suggest doing your first full backup directly to the USB drive, rather than over the network. This'll be a lot faster. You can then connect the drive to the base station, and re-select the image using the "Disk Image..." choice in SuperDuper!'s destination drive pop-up."

How is creating a sparse image wih SD different from using Disk Utility? Do I have to determine a maximum size in advance? (IIRC, I have to do so with Disk Utility.)
Can I create an AES-encrypted sparse image with Disk Utility and use that for backup with SD? I found this thread which seems to indicate yes, just would like to get a confirmation:
http://www.shirt-pocket.com/forums/s...ead.php?t=4744

As for the minimum system for booting up, mounting the image and restoring, it would *really* have to be sized down to the bare essentials. My backup drive's size closely matches my MB's drive size, so the backup image should match this size as closely as possible as well, not leaving much room for an additional OS.
Unfortunately, I can't find the 10.5 installer dvd for my laptop, so I would have to transfer the necessary files manually.
Any pointers to a tutorial how to do that?