What I typically do is the following.

1) If the water is flowing pretty fast, I put the weight (1-2oz or more) on the bottom and come up about 12 inches and then attach a side line with some cut shad or cut mullet.

2) If the water is running slow, I put the weigh about 12 inches from the bottom and then put the hook on the bottom with cut shad or cut mullet. This will allow the bait to slowly move with the water, but if you do this when the water is running fast, the bait will move too fast.

Also, once I see the catfish are eating more shad, I start using smaller to medium size shads and fish the whole shad. BTW, when I mean cold, I am talking about temperatures ranging from 50 to 30 degrees. This is southeast Texas and we don't get to ice fishere here....LOL.