MDT Media - StateStore on USB Deployment media drive?

Question

MDT 2012 update 1
I'm doing a Refresh (migrating XP to 7) using USB Media of my working task sequence.
Everything works, migrates to 7 with all user data etc..
However I noticed it takes a very long time. There's a "StateStore" folder being created on the USB drive containing the following:
USB:\StateStore\USMT\File\E$\Deploy\Applications\
USB:\StateStore\USMT\File\E$\Deploy\Out-of-Box Drivers\
USB:\StateStore\USMT\File\E$\Deploy\Scripts\
USB:\StateStore\USMT\File\E$\Deploy\Templates\
It contains some (but not all) of the folders from the USB:\Deploy\ folder. 
I still have a StateStore on C:\ containing the user data like it should...
but why would it ALSO be backing up some of the deployment folders on the USB Media drive?
After deployment completes, the USB's StateStore folder is never removed either.
I'd really like to reduce the time it takes by avoiding this useless backup, and potential problems that may surround it.
I have the following in my CustomSettings.ini, but nothing that should be causing backup of anything on other drives.
USMTMigFiles001=MigApp.xml
USMTMigFiles002=MigUser.xml
USMTMigFiles003=MigFMCNA.xml

Answer 1

Thanks for the reply!
I put in the following entry in my custom MigFMCNA.xml, but still have no change.
<component type="Documents" context="System">
<displayName _locID="miguser.avoidusb">Avoid USB Statestore</displayName>
<role role="Data">
<rules>
<exclude>
<objectSet>
<pattern type="File">D:\* [*]</pattern>
<pattern type="File">E:\* [*]</pattern>
<pattern type="File">F:\* [*]</pattern>
<pattern type="File">G:\* [*]</pattern>
</objectSet>
</exclude>  
</rules>
</role>
</component>