I've been having some issues sharpening my Becker BK7 on my sharpmaker. I can get the mid-section of the blade shaving sharp, but I am not able to get the tip or the edge very near the tip sharp at all - it's actually quite dull. Does anyone have any advice for sharpening a larger knife like this on the sharpmaker? I'm not sure if it's the length of the knife, or the curvature of the blade that is causing a problem, but I dont have this issue with any of my other knives.