Dick Westwood: I'm not sure what kind of a mast you have but will assume it is not "bendy" and more like a telephone pole. The backstay adjuster primary use is to BEND the mast in the MIDDLE thus taking the fullness out of the middle of the mainsail and flattening it, With a stiff mast, when you crank on the backstay adjuster, you are racking the mast aft. What the boat now thinks to itself is that the skipper has just moved the mast from its normal position to some point aft. When then happens is weatherhelm develops. In your case, you've indicated there is no sag in the jib and that is a good thing. The next question is how much can you crank on the backstay? Not much (the forestay is already tight) and you don't want too much rake anyway. How much is too much? The boat will tell you when you have gone too far as weathelm will develop. I'll bet a couple of inches off of vertical will do nicely. Experiment in small steps to see how it effects your performance. A lot of guys ask me why I say use small steps. It is the same with adjusting a carb on a car or your home shower. After you make the adjustment you have to wait a minute for the reslts. This is especially true on a sail boat which is slow to react. I was on a mates boat a while back and suggested an adjustment, which he made but he didn't wait for his results and made another adjustment. He looked at me and asked where is the big result I predicted. My answer was "you just went past it!!"