Yeesh. I'll hope that others with better backgrounds weigh in on this. My understanding is that you want that jib tack as low as you can get it, not higher. I would bet that your observed increase in pointing ability is entirely due to you finally getting a firm luff. Tack that sucker down and get a firm luff on it. Your slot should be controlled by a limiter or track on the front beam in combination with mast rotation. A good starting point is to have the leech of the jib about two inches off the spreader with your rotator pointing back at the front of the leeward daggerboard.