So you're measuring like this? That's completely different than where I am on my Boyer MKIV. My experience is to have the trap line measurement fall even with the rear port for light air and halfway between the rear port and the stern for heavy. I'm MUCH more raked back than this measurement and could really feel that having it measured at the port for 15knots was way over powered. The second I raked it back more, the groove was steady and I had great speed: