Use the models from one of the liveries we provide for download (not N692FE, N672FE, N652FE, N149UP, or B-LAP) You will see a psd in the paint kit called A300_ext_nose_gear_albd in that file the area of open space to the left of the nose gear markings will be the roof reg. If you’re not using it then just make sure it’s transparent.