The MEGA 360 uses the SI circuits. It REPLACES SI on a SI+ unit and ADDS SI to a DI+ unit.
The 360's are rotating Side Imaging transducers so they do SI or 360 but not at the same time.
There is no switch, Y cable, or menu setting that will allow connection/choice of the MEGA 360 or the Side Imaging piezos in a SI transducer.