Hi Chris, you might try zipping the file to make it smaller, or also since your question is about a localized region of the object if you deleted all the faces that were not in that general area that would make a much smaller file. If it's still too big you could use a cloud based file sharing service like Dropbox to host the file and then give the sharing link to it here.

It will be difficult to give advice without seeing the .3dm file though.

- Michael