I use a starting reference point and it usually stays like that !20190513_231226.jpg
Persistent odometer would be great. Even if the distance is measured in wheel rotations rather than kms.
the sensors both have to have weight on them and covered. Once you go over .5 mph you only need to cover one sensor to keep the board activated. See video and description below: https://www.youtube.com/watch?v=BSRbAf7obNQ