Connecting the XTM 9 QB 90 T to the "Dual Beam" leg of the AS SIDB Y cable would utilize only the 200kHz/83kHz 2d piezo in the XTM 9 QB 90 T ...
Connecting your SI xducer to the "Side Imaging" leg of the same AS SIDB Y cable would utilize the SI and Temp from the SI xducer ...
This will work ...(if this is the scenario you describe)...
Rickie