Help setting up virtual dual stick controller mapping

I have batocera setup on a Ser8 powered multicade unit with 2 8-button and 2 6-button dragonrise joystick controllers. This all works great for a variety of systems, but I’d love to be able to combine the joysticks from two controllers into a single “virtual” controller (if that makes sense) for dual stick shooters like smash tv and others. Does anybody know a way to setup mappings like this? So far I haven’t been able to map multiple physical controller into the same game controller for simultaneous use.