After about 40lb line things can get dicey on a kayak I've gotten hung up yo-yoing with 40. Crap, I could barely pull hard enough to break the line. And pulling was tipping the yak. It's also hard to use the heavier line becasue the fish will just tow the kayak instead of pulling drag off the reel. Like lowprofile said, putting your legs over the side helps with ballance and gives the yak more drag for the fish to pull. The position I have found to put maximum presure on a fish, particularly a big YT that is strait up and down, is to get the rod butt under my under my right thigh. I put my left foot on the gunnel of the yak and lay the rod on my instep. The rod is now parallel to the water with 3-4 guides strait down under water. With a fast graphte rod this really puts the hurtin on the fish. When I see a guide or 2 come out of the water I'll crank the reel until the rod is bent again. If my low torque high speed reel can't crank in line under the load I will reach out to the lowest guide with my left hand and pull the line to the reel. I do not ever pump the rod in this technique. In this position I have a low center of the gravity and the line is very close to the side of the kayak but will not touch because of my foot. It's sort of a kayak version of east coast tuna fighting style(vid 1) and long range rail fishing(vid 2). I rambled a bit but I hope you get an idea of this technique as I have never seen any one fish like this.
http://www.youtube.com/watch?v=4WUVlPIWpdc
http://www.youtube.com/watch?v=cz7Gi...feature=relmfu
Mike