I thought most or all Salmon trolling was down deep? I dont really know much about salmon fishing other then I like to eat them raw with sticky rice and Wasabi
Looking at your set up I would think either on the two flat bridges running fore and aft on the radar arch the only issue is you would have to climb up on something to access them unless they came thru as the more expensive outrigger mounts do. with 1/8" plates you may need a welder to reinforce it just a little. A better spot is where the window ends on your gunwale (both cheaper and easier to use) , looks like you have a rod holders there already. I would mount them there personaly and run 15 OR 16'. I have 16' on mine and think anything longer would be a PIA