Preseeding LVM over software RAID?

[Brice Figureau <brice+debian@daysofwonder.com>]

Hi,

I'm quite new to preseeding (but used the d-i several times before
that).
I'm trying to setup a preseeding installation for a LVM over 3 software
RAID1 partitions, I mean something akin to:

/dev/sda1 + /dev/sdb1 -> /dev/md0 ext3 /boot
/dev/sda2 + /dev/sdb2 -> /dev/md1 swap
/dev/sda5 + /dev/sdb5 -> lvm VG, furtherly splitted in several LVs
for /, /home, /var, etc...

Since it doesn't seem to be supported directly by the d-i preseeding
system at this time (ie you can choose anly between "regular", "lvm",
"raid" and "crypto" for partman-auto/method), what would be the best
option for me?

Should I create a shell script that setup my partitioning and software
raid devices first (a kind of early_script), which then let
partman-auto-lvm do its job, or is there any other possibilities?

Thanks,
-- 
Brice Figureau <brice+debian@daysofwonder.com>