I have been a lowrance user for years, and recently garmin for the panoptics for ice season, last year i put a terrova t/m on the bow, they are basically set up for hummingbird as you probably know, I was going to replace my hds 8 up front with a helix model, but as I am looking it seems you have to choose either DI or SI, Am iI right in thinking you have to choose one or the other when buying these units, my lowrance and garmin have both built in.

