Garry, I believe one of the roles of the two Majors would have been to command a wing of the battalion, if the battalion was required to operate in two wings. When the Light Division was split into 2 brigades, the 95th Rifles was split, Right wing joined 1st Brigade and the Left wing the 2nd Brigade with the Majors in command.
Another example is the 1/52nd, it operated as 2 wings [partly due to it's size] in the closing stages of Waterloo. Paul