There is something left of the SI xducer that the left SI beam is reflecting off of - jackplate, live well screen, trim tab, another xducer, ladder, sponsor, etc ...
The SI beams reach all the way to the water's surface on both sides ...
The DI image in the HELIX 5 SI is derived from the data received by the SI piezoes and then computer generated into a DI "looking" image ... so any echo showing is SI is also going to show in DI ...
Rickie