Ok here's how it works currently. for me at least.
If you boot a MD from a fresh install. It will not pxe boot, it fails looking for a config file iirc.
If you run /usr/pluto/bin/Diskless_BuildDefaultImage.sh
It should now enable the pc's to boot.
You should see announce to router
Alot of MD's will fail while running the Diskless Setup ..... this is due to the lack of a 64bit diskless image.
After the diskless failure you will have an entry for the new MD in web admin.
Change the Arc to i386 select update, then press the rebuild image button.
Once finished the web admin will say so.
At this point the directory structure should exist for that MD.
Follow the 0810 MD instructions regarding the password and updating of drivers.