Virtual Vault, Approximate Size of .MDC file for meta-data only.

I thought this may be of interest to anyone deploying Virtual Vault (VV) in their environment;

We currently have VV setup so that only the Meta-Data is stored in the local Vault Cache (within the .MDC file), i.e. not the full archived item.  NB:  This is only for desktop users.  Laptop users will have access to full items via Vault Cache.

Anyhow, as a rough estimate (after some initial testing),  you could say that the avg. growth of the .MDC file is;
 
~5MB per every 50MB in the users archive

I needed to know this Avg. for our storage guys as we are placing our .MDC files on the SAN (locally on the C:\ is not an option, plus if multiple users logon via hotdesking, it could get messy).   Please note this is an approximation but may be useful to someone else? 

If there's an official set of numbers then please post a reply ;)  Obviously, for users with laptops and full Vault Cache items downloaded to their C:\ this will be significantly different. 

Thanks,
BZ