One thing I have found to help is to not swing the instant a silver grabs a plug. I like to crank down on them, then swing. A coho is generally chasing down a plug so his momentum may carry him foward, creating a bow in the line in the time that you are realizing he is there, and then you are swinging on slack. If you remove that little bit of slack by cranking you'll set solid. When trolling the boat pulls the slack out before you can get the rod out of the holder. When you are in a current situation, the fish probablay grabs and drifts back with the current, pulling out the slack. Well at least that is how I imagine it in my head.

Here is a video of a fish taking a trolling herring, you can see his momentum moving him forward as he grabs it. LINK If you are in a stationary boat, you have to load up the rod, like you are trolling.

There is a difference for sure between trebles and singles, in that i feel the siwash can twist flat, and come out of the fishes' mouth. That unfortunatly is unavoidable.