From what I know about aerodynamics, & from what I have seen with models of large Pterosaurs like Quetzalcoatlus, these animals could NOT fly as shown in this video. They would be far too front-heavy. One solution to that could be that they bent their necks up in a kind of 'S' shape. Another idea I thought of is maybe they flew with their head sideways with their crest acting like a lifting surface. Or maybe they had a skin membrane stretching from their wings to their neck to provide lift.