That's the thing Phil, you never know where the fish are.
They could be cruising around just under the surface a few yards out just where your line enters the water, they could be a foot in front of your bait mooching around the bottom, they could be swimming around 4 feet down halfway across.
You could spend all day experimenting and not get anywhere. I just look on it as it's nice to know there are fish out there somewhere.
I've never had a liner from one that's swum around the back of my rig though.