parsifal
Colonel
If ther p-38s were being assigned the 'bomber escort ' role, whilst the P-51s were being assigned the Free ranging, fighter killing role, that would be consistent with most airforces. The aircraft with the lesser ability to take on enemy fighters would be assigned the role of final defence, to add firepower to that inner ring defence zone. It may also have something to do with the distinctive shape of the p-38....hard to mistake the profile for an Me 109....just my two cents worth