Can't add new file extension to app's document types

FROM : Rick Mann
DATE : Wed Apr 02 20:32:59 2008

Hi. I've already reported a bug for this reproducible problem, but I'm 
hoping someone can suggest a workaround.

I created a Core Data document app from Xcode stationery. I then added 
a second file type to the target properties inspector so that it would 
open ".gpx" files. However, if I choose Open, the nav dialog comes up, 
and all .gpx files are grey. An Apple engineer sitting next to me last 
night was able to reproduce this problem, and so I filed a bug, but 
surely others are not stuck by this? It's kinda keeping me from doing 
any more work on my app.

Has anyone been able to make this work (adding new filename extensions 
to the list of an app's supported types)?

TIA,
--
Rick