Nice map Mouse, and thanks for the mask - that makes life easier !
The map size in RAM may be to do with a couple of reasons. It could be the undo allocation or it could be to do with the format that the file is store internally. There could be a number of sensible reasons for it but my experience has been that windows stuff is pretty bloated on the whole. To be honest I find almost all apps from everyone to be more bloated than they need to be.