I'm thinking about putting a RAID 0 in my 15" unibody MBP. Right now I boot off of a ExpressCard 48GB SSD, which is really fast, but of course it's not that big. I figure that the array would be quite good at handling large swap files, but I don't believe OS X will just use other drives mounted in the system, but I wondered if I could ask it to do so, much like you can with scratch disks in Photoshop. Ideas? Thanks!