Adding ac, what should I do with my fantastic fan.

This is just a thought, but adding an AC unit to the hole that is wired takes very little time. Maybe 30 minutes, once you pull the Fantastic Fan and clean the cauk around the hole. Try it there with the Fantastic in the bathroom (or simply hold off on mounting the Fantastic until you try your camper with the AC over the cabover). If it works out okay it sure would be simply than cutting a hole, running wires, etc.

My two cents