The Windows Server Performance team has updated teh Window Server 2008 Tuning guide to include Hyper-V.  The Hyper-V section provide a lot of recommendations you will find useful.

Check it out below...

http://blogs.technet.com/winserverperformance/archive/2008/06/17/power-and-hyper-v-are-now-part-of-the-windows-server-2008-tuning-guide.aspx