The FAA does not require your registration # be visible, only accessible without tools...First off let me say I am registered with the FAA. The registration is for the individual, not the UAS. That said if someone has your registration # they will be able to eventually search the FAA site and acquire your information. Now a possible scenario, somebody with motives to use a drone for illegal purposes has access to your registration # and they ID their drone with it and the drone is found, somebody will be knocking on your door and you’ll be in a position of having to prove your innocents. DON’T ID your drone with your # visibly.