Reading Don Brown's AvWeb column, filing to lat/lon's is causes problems.

Stan Gosnell wrote:
You can file to any fix you can navigate to. I regularly file to and from
lat/lon coordinates, far from any airway. It's easier for ATC if you file to
a fix they have in the database, but it's not absolutely essential. You do
need to be able to navigate to the fix in the event of radar failure.
You may not be cleared to the fix you filed to, and perhaps won't get the
route you filed. But you can *file* what you like.