Spoke to a doctor friend of mine (sports medicine) about this. According to him, it is possible to do a reverse prayer, elbow-to-elbow - but only for a woman.
The structure of the shoulder girdle in men and women is subtly different. The range of motion for men is such that going Elbow to Elbow would dislocate one or both arms. The slight restriction on movement is part of the price we pay for our greater strength - the slightly different structure provides greater leverage.

Also heard from my Yogic friend - who will not be helping with this challenge, as she just gave birth to twins!