If one buys the double suicide or murder/suicide scenario, they could have hung the belts/ropes from the railings, secured their arms with the jackets and then simply laid facedown placing heads into belt. the belts would obviously have been set to constrict their throats but gravity might do that....... It would explain the straight legged posture. I believe thats how L'Wren did it, from a doorknob.
It seems like that wouldbe very difficult. Just like trying to get that appleon a string. The childrens game where one tries to bite an apple hanging from a string.