I don't use a scale to set my drags and just sort of do it by feel. A heavy drag is some times not useful on a yak cause if the fish runs out it will tow the drag of the yak enstead of the reels drag and when the fish is straight down you can feel tippy. How are you fighting your fish? I have found a a technique that I use on all big fish (YT) when they are straight up and down. Kayaks have little latteral stability, obviously, and much stability bow to stern. This means the farther you hold your rod to perpendicular off the side the less stability you have. It looks kinda strange and I have never seen any body do this but me, but I sit on the rod, put my left foot on the rail, and lay the rod across my left instep. The tip of the rod is now just a few inches off the side of the yak and close to the bow. The most stable position. Further, with the rod in the lowest posible spot right above and paralel to the deck the center of gravity is as low as it can get. Again mors stablility. I do not pump or lift the rod at all. When I see the rod begin to recover, lose its bend, I crank the reel and grind a bend back in to the rod. Ths puts constant and heavy presure on the fish, even when liftin/dropping on swells, and never lets slack in the line like lifting a pumping some times can. I came up with this idea as a sort of kayak highbrid of these 2 styles, east coast giant blue fin fishing and west coast long range rail rodding.
http://www.youtube.com/watch?v=_C7ZcDnIW_w
http://www.youtube.com/watch?v=z1DGQNEpTLM
When my reel has lacked the torque to crank a bend in to the rod I have used the east coast style of grabbing the line at the stripper and pulling it in to the reel. Long post but I hope this helps you fish a heavier drag. Works for me. Mike