I usually set mine 2 over the speed I'm going
when I'm trolling around pulling cranks of checking out a location to see whats there. Just remember that if you're running the chart speed slower, what you see on that chart is further behind you than it would be if the chart was faster. Yeh, you'll get a clearer image but it's further behind you in real time. If you're not marking a waypoint and trying to refind it when you turn around, it'll be tougher to locate it again if you're looking at a certain stump or something visual to re find it. I pull cranks at 1.8 to 2.2 MPH and leave my chart speed at about 4 or 5 and get a very clear pic. It is awesome though when you have someone in the boat with ya and you see a fish on the DI below you and tell them to watch a certain rod, it's fixing to get a hook up and it does!!!