Help with setup of iSCSI and Hyper-V

I have a server running Hyper-V server 2008 core edition, and a QNAP box providing the storage via iSCSI.  I've set up multiple LUN's in the QNAP box, and mapped each LUN to a drive letter on the server, so that each virtual machine has it's own drive letter.

Is this the best way to do this, or would it be better to have one large LUN as a single drive letter, and put all the virtual machines on this one driver letter - if so, would they be better in sub folders, or all in the same folder?

Thanks in advance.....