for a human to fly, as an example of mothman size, we would need a wingspan of roughly 25 feet, (that is why most hang gliders are at least 30 feet across at the minimum).. but, and this is a big but...lol. as the wing span gets bigger the weight ratio increases resulting in the need for an even larger wingspan, so a vicious circle kinda thing.. now, if mothman exists in the physical world, maybe he is more birdlike, hollow bones, lite weight, etc... but even then the muscle needed for flight (which is dense and heavy) would come into play. so the question of maneuverability and speed is a valid question to be asked. most pterosaurs were gliders that rode the winds, not easy flyers. most descriptions of mothman having a 10 to 12 foot wingspan just wouldnt work.