I fish for Stripers, crappie and occasionally white perch. At times shallow in 5-10 FOW. I use an HDS 9. I'm no expert yet, but here is what works well for me on the Structure Scan (SS) settings. 1). Use the full screen width. I set my panels such that the SS is all the way across the bottom. (See pic below of large school of crappie). You need to utilize the full pixel count to see the most detail with SS. I'm willing to sacrifice how long the info stays on the screen. Can always roll it back up if see something interesting. 2) Set your SS width at 3 to 4 times the depth. If in 20 FOW, I'm scanning 80 ft each side. If in 5 FOW, I'm scanning 20 ft to each side. Adjust scan width as depth changes. 3). Use 455 kHz when searching (most of the time). Use 800 kHz when you have found something and want a closer, more detailed look. On my unit, the 455kHz gives me brighter and farther coverage, in general. 4) Other than the scan width and frequency, run the other settings pretty much in Auto (contrast, etc). 5). Look for FISH (bright white images, schools, "submarines", etc). Look for SHADOWS, they indicate suspended fish. Fish where the fish are, not just where the bait and cover are. 6). If running more than 10 mph, I just use 2D sonar to give me a good bottom indication. SS works best at less than about 7 mph for me, 4 to 5 mph is ideal.

Hope this helps you some.

Tight Lines!