My buddy uses them for bass. It might work on Lake O for trout and salmon. I would worry about the hardware holding up to the stress of a big king. Another worry would be the other lures hooking the fish outside the mouth and making them fight sideways. Ever hook a king on a stickbait and it has one hook in the mouth and onither in it's gill plate? Makes a small king fight like a 40 lber.
I got 5 of them last season. Only downfall is the placement of the line counter. Other than that, there is not a better reel for the $ IMO. The drags are super smooth and adjustments are more fine tuned than other brands (Tekotas).
Buy the 50/200 kz transducer for the Lowrance and run it on 50 and the eagle on 200. Tilt one transducer back so you can see your downrigger weights at all times. You can put your rigger weights just above the fish. If you have both on seperate frequencies you will not have any interference.