I don't have manual downriggers any longer and if you're really into Salmon fishing, on a bigger boat you will move up to electrics quickly.
Both the higher end Scots and Cannon are really nice with built in pole holders, I also have an older Cannon that we still use, the mount isn't hinged and is sometimes a pain. But overall it's better quality downrigger than my Scots, with both up and down electric and free wheel controls, counter and 48' boom.
The Scots have a superior mount, which swivels fore, aft, and tips up to retrieve the ball and line which is really a nice feature with 60" boom.
Just don't buy a downrigger with a short boom. You need to keep the downrigger wire away from the hull and running gear on turns. You don't want that in your prop. It's a good idea to use Spectra downrigger line instead of SS wire.
Good season coming up with good silver and pink salmon returns forecast!!
Larry B