Pterosaurs - manoeuvrability
Less stable flight requires good control to compensate for the instability, but it can provide more manoeuvrability. Thus it would seem that some large pterosaurs had highly stable wing configurations, and probably did a lot of soaring like eagles and vultures, whereas others were probably capable of more dynamic flight. These animals would have had to have raised the tips of their wings above the body to achieve a stable, glider-like flight.
In aeroplanes, heavy transporters like the Hercules or Antanov have their wings above the fuselage, whereas fighter planes like the Spitfire have their wings under the fuselage. However, those with the less stable wing configuration could simply elevate their wing tips to achieve a stable configuration if necessary, thus becoming a glider.
In the head, the part of the brain that controlled flight was enlarged, and the eyes were also proportionally large, as good visual acuity and spatial awareness is essential for daytime flying. Formerly it was believed that pterosaur head crests stabilised flight. Certainly large crests would have had an aerodynamic effect, but it may have been detrimental, and in reality the crests might even have hindered flight, in much the same way as a peacock's tail.
Today we hypothesise that the crest's role was more important in species recognition and perhaps in sexual display. Certainly some crests became excessively large, as in Tapejara where the crest can be three times as large as the skull itself.