All my Custom fields for Z2-Running are now public. The script can easily be adapted if you want the same parameters for other zones. If you create one or more Fitness charts with these parameters, following up on your performance becomes visible and you can see which of the parameters is evolving/stagnating/deteriorating. Here’s a screenshot of my (poor) running ( better call it slow jogging 
) abilities that I have been working on for the last 12 weeks.
Finally after over 10 weeks, I see that all my work below AeT starts to deliver. Running technique suddenly got better and I don’t know if it maybe has to do with a long Power Hike I did around that date. Hiked for a little under 5 hours at sub 10 min pace over 30.5 km. I do notice that I jog more fluently since then.