I ran into the same issue setting up my HTPC, and the the short answer seemed to be no. The long answer, some people have gotten it to work, but it primarily depends on what you're using for a RAID ...

I put 2 250 GB HDs in the MP bay and chose both in what I hope is RAID 0 configuration (Mac os called it striped. Checking on the wiki these two terms seemed to be the same. (I want speed!) But now ...