As high as you have those poles you would be missing you target depth. Your boat speed, size of lure, size of bill on the lure, and diameter of your line. Very easy solution. Troll a line at the 75 feet across a point. When your contacts the bottom make another past deeper. When you no longer have contact with the bottom you will know exactly how deep your lures are running. This way you will know if have to, leave more line to reach you're desired depth.