Finally got enough wind to continue testing yesterday. I have found some circumstances where the datafields have recorded high values in the alpha and NM fields. I have tracked this down to the watch failing to provide GPS data when it is requested, this leaves the old values in the array which messes up the next calculation. I have written code to deal with this situation for all categories in all 4 datafields.
It appears that when I release a new version of a Datafield then all users have to do is sync their watches to Garmin Connect on their computer and the latest versions will be downloaded automatically (This is the default in Garmin Connect). I don't think the datafields are updated automatically through Garmin Connect Mobile.
I have also changed the order that the results appear in the stats panel. So you will be able to tell if you have the latest version if you see the results in the stats panel ordered as 2Sec, 5*10, 1 Hr, Alpha, NM