I'm afraid you'll currently have to add the extra call to TrackFeature() as you suggest.
This will be improved in two ways in our next major update scheduled for this fall: 1) for each timing there will automatically be registered events for Start and Stop (or Cancel) so you actually get the functionality you're looking for right out of the box and 2) we'll also let you customize the charts and their presentation in a more versatile fashion than now.
So: you're welcome to add the call for for now, but this kind of tracking will be automatically available in the not too distant future.
(btw, nice meeting you last Sunday :-)
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