I tried the HB model with downscan and all I got was trouble with water intrusion, and corrosion
. They were frustrating to deal with.
I eventually ended up spending a little bit more for the HDS 5 when they first came out. They have been slow to respond, but they did make sure that the maps issues were corrected. I do not know the limitations of the structure scan technology but I will say that I cannot imagine ever needing more than the stock HDS-5 for fishing big game in LJ. A standard 50/200 ducer works very well for me, but some feel the higher frequencies provide better detail in shallow waters, the deeper waters do better with the lower frequencies. Although the side and down scan technologies are cool, they are better off being used to find bug structure than fishing for big game... and at $600 for the add on module and a second ducer to worry about it seems a bit much for a yak... so save the money and go buy a new reel!
my 0.02