Complex sentence: The fuselage was strikingly clean aerodynamically, with only gradual changes of cross-section from nose to tail, where the rear the horizontal surface, mounted on top of the fuselage, had both a high aspect ratio and marked dihedral.
Split into simpler sentences: The fuselage was strikingly clean aerodynamically, with only gradual changes of cross-section from nose to tail. The horizontal surface, mounted on top of the fuselage, had both a high aspect ratio and marked dihedral.