Got Turtle Sports up and running fairly easily. i successfully added (recent) historical (.fit) data manually, but TS wanted to pull files automatically from a much older Garmin folder rather than the one my Garmin xt310 currently uses. That means I'll need to add all my ongoing data manually - no biggie, but hardly ideal. There seems to be no way to configure which folder TS automatically pulls data from by default. And there's so little support documentation out there. All of which seems a shame because the way the data are accessible, viewable and manipulable suit my needs.
Guess I'll have to give MyTourBook a shot.