Obviously you never had a kingsnake... I had one that that would eat itself, then realize what it was doing. Snakes are not the smartest when it come to judging prey. Either way, the general rule of herptile-keeping is: one specimen per vivarium. Fights occur, cannibalizing occur, hunting occur, stress occur, and oversexing occur. Oversexing is a big concern when males mature earlier than females.
Either way, even if you do manage to keep 2 boas without any injury, one will be so stressed out to the point it will die in a couple of years.