[CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

I'm trying to setup a very small system intended for doing
monitoring/logging. It's done on an Intel Atoms in a small box and the
idea was to simply run it off a pair of USB flash drives in software
RAID 1.

Now the problem is that while the 6.2 DVD installer could go through
the entire install process, grub will load then just stop at the
prompt. The system will work if I use a SATA hard disk so motherboard
compatibility is not an issue.

Attempting the various methods to re-install grub (via rescue mode) or
using the grub prompt to setup the disk does not work either. grub
just does not seem to be able to find the USB drives. e.g. commands
like root (hd0,0) just says device not found. This is despite grub
having just loaded from it and despite that grub-install in rescue
mode does not report any error.

Same problem even if I just go with one USB drive in a plain vanilla ext3 setup.

It seems that some sites are saying that EL variants just don't seem
to be adaptable to installing and running off USB drives. Is this
really the case and that I should be looking at using another
distribution or am I just missing some crucial steps in the process?