Is it necessary to use both SMA RF antennas on a GX440/ES440

We are using GX440s with a Rocket Utility antenna that has a single Verizon connection mounted on the roof along with a GPS and WIFI leads. What should we do with the diversity MIMO interface? Can we plug a small stubby antenna into it even though it will be inside the vehicle and not roof mounted? At his time we cannot run new antennas to the roof since we did not realize 4G required dual antennas and the antennas were supposed to be for 4G modems.