I used that same method for years with Mapsource and my 276C. Since I got my Montana and have done the same thing with Mapsource (I do save routes as gpx and copy to Montana) and also have done the same thing with Basecamp and used Basecamp to copy the routes to the Montana. Basecamp has some advantages, but saying that, I have not had any limitations using Mapsource with the Montana for my purposes. Edit: When routing, I use waypoints in intersections and have never used direct routing. For the way I use the Montana on trips I never use tracks. It all has worked without problem for me. My routes have never changed on the Montana from which ever program I used to create them (Mapsource or Basecamp). YMMV, but it has worked for me.