I scaled the X and Z size ~115% to fit the lights were purchased from Amazon and also enlarged the screw hole for #8 drywall screws.   

Designed to fit these 22W lights from Amazon.  https://www.amazon.com/dp/B07XJXPWFL

Remix of the light_mount_rear_mountv2.stl file from https://www.thingiverse.com/thing:2798751