Booting from ISO in Xen Paravirtualized Environment

Booting from ISO in Xen Paravirtualized Environment

Specifically, Citrix XenServer 5.6.
I can map the an ISO from a Storage Repository with no issues and mount it
inside the OS but I can't boot from the DVD drive without converting it to
HVM, which causes problems because the ISO I'm trying to boot from is a
"Bare Metal" restore so it's a tad bit sensitive to whether it boots into
paravirt or HVM mode (for example, former uses paravirt drivers for
primary HDD at /dev/xvda whereas the latter puts primary HDD at /dev/sda).
I've looked online and the only thing I've been able to find are
instructions on how to boot from ISO by converting to HVM (which works for
the boot, but undercuts the reason for the boot in the first place).
I've looked around without much luck on how to configure Citrix's PyGrub
to boot from ISO. No joy on that, and the only PyGrub examples I've found
don't look like they're going to play well with Citrix and are far too
manual for that to be our SOP in case of disaster recovery.