I first removed the steel cable from my Cannon Lake-Troll and replaced it with Scotty 250 pound Dyneema braided downrigger line. The Dyneema eliminated the irritating hum from the steel cable, but replaced it with a problem which I hadn't had when using steel cable - I got a sonar return from the braided line which created extensive streaking in the upper portions of the water column on my sonar screen which made it impossible to see if there were any fish in that area. I complained to Scotty and about this problem and was told that nobody in the universe had ever encountered this problem but me, which I doubt. So I switched to Scotty 175 pound low drag Spectra braided line, which also eliminated the hum problem, and creates little or no sonar return. I've been real happy with the Spectra downrigger line.
A problem I had with braided line which I didn't have with steel cable is that some times when transporting my downrigger, the braided line would come out of the groove in the pulley and get stuck between the pulley wheel and the side of the housing. The only way to get the line back in the groove is to cut off the snap, pull the braid back through the groove with a pipe cleaner or other stiff wire, and tie the snap back on. This is a pain in the butt. Cannon should re-design its pulley to prevent this from happening. To prevent the braided line from coming out of the groove, I keep the line under tension when I'm transporting the downrigger, by hanging the ball on a hook which I've installed on the base of my downrigger. Since I started doing this, I haven't had any problems with the braided line coming off the pulley wheel.
At the end of the braided line, I use the standard Scotty terminal kit, which includes a snap with a swivel and a bumper, tied on with a Palomar knot. I worry about bringing my downrigger weight up too fast and busting the downrigger line when the weight slams into the downrigger pulley. But it's easy to avoid that, because if you watch the line as the weight approaches your kayak, it's obvious when it's only a few feet below the surface, so you can crank more slowly. If you're worried about wear on the end of the braided line, just cut off the snap and re-tie the line, which only takes a minute.