https://www.hq.nasa.gov/pao/History/SP-468/ch11-5.htm
Says this in paragraphs 5 and 6:
“
A large anhedral angle (negative dihedral angle) of the horizontal tall in combination with a sharply defined positive dihedral in the outer wing panels are two conspicuous identifying features of' the aircraft. These two features are related to the position of the exhaust nozzles located only a short distance behind the low-mounted wing. To avoid impingement problems with the hot jet exhaust, the tail surfaces are mounted on an aft fuselage extension above the nozzles. As indicated by early wind-tunnel studies, the resultant high position of the horizontal tail in combination with the wing-shape parameters led to undesirable nonlinear pitching-moment characteristics at high angles of attack. The large anhedral angle, or droop, of the horizontal-tail surfaces greatly improved the pitching-moment characteristics, as well as increasing directional stability. To achieve the proper balance in dihedral effect for the integrated aircraft configuration, however, a large positive dihedral angle was incorporated in the outer panels of the wing. In addition, the wing dihedral elevated the wingtip vortexes relative to the horizontal tail and further improved the pitching-moment characteristics of the aircraft.”