Use of VIrtual Machines in Foresnic Classroom Training...?

Hi Folks,  I was wondering if anyone out there involved in Forensic Training is using VMWare/VB in the classroom setting.  I have been generally limited to using USB Drives due to size/time/cost limitations for the students.  I would LOVE to be able to add a "Hard Drive" to a VM and size it like 8gb and maybe format it Fat32. Then have the students create/delete files to look at what the file system is doing. 

   I can do this part easily,  but in creating a forensic image of the VMDK I don't get traditional un-allocated drive space (to practice carving etc..).  I may not be imaging the Virtual Disk files correctly.   

 Does anyone do something similar or use VM's in the classroom setting and have any tips or suggestions on how I may take advantage of Virtual Disk's in forensic training? 

Thanks for your time..   😉

Rob