DOSBox: Configuring Two XBox 360 Controllers

I’m trying to play a two player D.O.S. game. The only way I can figure out to remap the controls for the first player is set the controller, XBox 360, to keyboard. Then I get a bunch of Auto options, which I can use to remap the first controller but this doesn’t work for the second as there is only one set of Auto options even if both controllers are set to keyboard. What am I doing wrong here?