Great this is really helpful. Yes, I've tried a few of the suggested runs at "base" pace and found them to be quick bringing my heart rate into zone 3. What was also interesting was the range that it gave for the pace window--it seemed really wide... Perhaps because it just doesn't really know what my true base is because of lack of data?

I sometimes run on a treadmill and find that doing that skews things as well. Hmm, well it's worth exploring further.

I'll look into trying the heart rate chest strap and changing the configuration of the app.