Best setup for RAM drive

Hello,

I need some insight on the best way to use a RAM drive in a Postgresql
installation. Here is our situation and current setup:

Postgresql 7.2.1
Dual PIII 800
RAID 5 SCSI disks
Platypus 8GB PCI QikDrive (the RAM drive). http://www.platypus.net

The Platypus RAM drive is a PCI card with 8GB of ram onboard with an
external power supply so if the main power to the server goes off, the RAM
is still powered, so it's persistent between reboots.

Currently the disk size of our database is 3.2GB, so we put the whole
pgsql directory on the RAM drive. Current preformance is very
snappy with the bottleneck being the CPUs.

The concern of course is if something happends to the RAM drive we are
S.O.L. and have to go to the last backup (pg_dump happens each night).

The other concern is if the disk size of the database grows past or near
8gb, we would either have to get a bigger RAM drive or somehow split
things betten SCSI and RAM drive.

I don't quite grasp the full inner workings of Postgresql, but
for those of you who obviously do, is there a better way of setting things
up where you could still use the RAM drive for portions of the pgsql
directory structure while putting the rest on disk where it's safer?

Should we just put pgsql/data/pg_xlog on the RAM drive?

Also, in the very near future we will be upgrading to another server,
pg7.3.2 with dual P4 2.4 xenon's. The RAM drive will go into this new
server.

Any suggestions?

Thanks

Chris