MPI Virtual Cluster via usermode linux... Possible?

[Fillzee]

I was just wanting to brush up on my mpi programming skills. Since I don't currently have access to a cluster I thought that maybe using several instances of usermode linux (8 to 16 instances) with a base gentoo system would be useful as a cheap mpi testing tool. Has anyone ran 8 to 16 instances of usermode linux at the same time? I'm concerned about if my machine can handle running all these virtual machines concurrently and still be usable. Also any input on installing and configuring mpich would be helpful.