Have to weigh in on this one. I worked with bison for 34 years at a national park. Having seen them killed with all manner of weapons; from large bore rifles, shotguns, pistols, vehicles, helicopters, bow and arrows; I believe a well placed arrow will kill more effectively than all the rest. As said above, study the animal for arrow placement before shooting and put in arrows until the animal is on the ground. Your setup is plenty good.
IF they decide to kill it with a gun, 12 guage slug right behind the ear is the fastest.