Most instructional miss the mark. " here is the halfway point". That's supposed to be the sweet spot, but its in error. Balls don't come off rails at the same angle as from coming in. It works fine with lasers and mirrors, but balls and rubber don't react the same way. There's deviation depending on where the cueball is struck. Top spin off a rail won't be the same as bottom. Mirror image is nothing more than a good starting point, but natural feel will always be more accurate. You have to reach that point,of course, but most bank systems fall short. Maybe its the beer talking.