Fender used some seriously unstable pearloid on those basses. By the early '70s you find Comp Mustangs with 20+ pickguard screws from the factory, just to keep the things flat.
The D and A strings are perilously close to the height adjuster screws. There is something a bit suspect about the geometry of Mustang bass bridges. The bridge is a clear influence on the first Stingray bass bridge. Leo Fender took some ideas from the Stang to the Ray. For being a budget instrument the Mustang is richly appointed.