You can change the layout of the Garmin device screen in Eclipse. For example, set 5 fields for an Edge 820 device. Or whatever. Nice.
Except then your data field runs in ALL the fields. That is not normal device behavior, and causes onLayout and/or onUpdate to run several times every second. Generally not an issue, but can cause behavior that is different from a real device in which you assign your DF to one of the screen's fields.
Just a suggestion that you run a DF in one of the one screen fields, and possibly allow the selection of which it runs in.
-- Dave