XFS External Log on Pg 7.4.8 Pg_xlog drives?

Fellow Postgresql users,

I have a Pg 7.4.8 data on XFS RAID10 6-disc (U320 SCSI on LSI MegaRAID
w/bbu). The pg_xlog is on its own RAID1 with nothing else.

I don't have room for more drives, but I am considering moving the XFS
external log of the data directory to the RAID1 where the pg_xlog
exists. Unfortunately, I don't have room on the RAID1 that the OS exists
on(Centos Linux 4.1).

Anyone have any experience moving the XFS log to the pg_xlog? The
guessing the the benefit / cost will cancel each other out.

Thanks.

Steve Poe