Wait till the mover travels to the end of the track.Take a measurment for your flex. Put the flex on the hood with a stainless steel clamp.Use a bungie to hold it up. Don't wrap the bungie around your flex,just let it relax on top of the bungie. That way your light will travel back and forth with ease. I have a 4 foot hydrofarm light mover. :thumbsup: