Sonar/Down Imaging question

[dooma_Flatchy]

I Just got the humminbird 597 hd di unit and I went and tried it out(mostly played with it) Saturday and I was wanting to know what setting most people use on their chart speed for the 2d sonar and down imaging for fishing? I fish Lake Guntersville, relatively shallow lake with the max depth around 60 to 70 feet along bluffs, Lots of humps and grass grass grass.