Hi there,
i'm in doubt whether this will work - following the link doesn't download
the file (in the sense of a http GET) as it should, instead it shows
the file contents on an edit page... well, as said, just try it. 
Anyway, don't remove the folder setting - the plugin will save diagrams
and track infos in that folder, so it should be there and also be writeable.
groetjes, Frank