specifying content types when uploading files with WebDAV

Whenever I upload text files into Plone with WebDAV (WebDrive) it tags them all 
as "Documents" when I need them all to be "Portal Files."  I'd add these text 
files through the Plone interface, but I often have to upload them 100 at a 
time.  

Any ideas on how to make sure that all uploaded text files get tagged a 'file' 
and not a 'document'?



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