Pass Through disks are ideal in situations in which you need to exceed the 2 TB capacity limitation of the .VHD format. In using a Pass Through disk, you will not have the ability to use snapshots. The maximum size for a Pass Thru disk is???? Unfortunately after a long Google and Bing session, I could not find this answer. I did find an article about an organization that linked (6) 2 TB hard drives and created a 12 TB pass-through disk that was functional. I also saw that during some maintenance, they had a problem getting the VM back online.
As always, test before putting a new configuration into production.
Please post your maximum Pass Through disks sizes here and tell us how successful your implementation has been.