A point to consider during your investigation ... :
HB has the capability of mounting an imaging xducer on each side of the boat with the 9 M SILR Y cable ...
https://humminbird.johnsonoutdoors.c...splitter-cable
This would allow left SI to come from the port mounted imaging xducer and right SI/2D/Temp to come from the starboard mounted imaging xducer ...
Of course this means the purchase of an additional imaging xducer ...
But it eliminates SI blockage from the lower unit completely ...
Rickie