Maybe a backup program like Retrospect run within the virtualized SL and pointed to the SL partition through the Shared Folders would do a duplication?
UPDATE: I have no experience with Super Duper, but I have used Retrospect over the years to make a duplication of one hard drive to another.  
1.  Will Retrospect work within vSL?  I just used v6.1 and it runs fine in vSL.
2.  Will Retrospect duplicate from a Shared Folder?  Yes, I was able to duplicate a folder in my Lion environment to vSL.
3.  Will Retrospect duplicate a complete SL Partition?  I do not know, as I have no real ability to experiment and try this.  The question is whether or not it will move System files from a Partition into the Active System Folder of vSL.
One way this would work for sure, is to use the backup copy of the Mac OS X Snow Leopard.pvm file that I always suggest every user make.  in one of my troubleshooting notes, I point out how to use the backup to then access the main .pvm file used for vSL as a second mounted HD.  Retrospect would then be run and move all files over.
Do you have access to Retrospect?  I think I have a trial version somewhere in my collection of software.
My Dad still talks about eating Ole's Chili as a child in Chicago; he will be 95 next month.  I often bring some chili over for dinner (I go over with dinner every Sunday), so he will enjoy it, too! 
					 
				
			
			
			
		 
		
		
		
			
			
				Last edited: Dec 13, 2012