Ok guys, after watching some Youtube of Karina's 1@41 and being totally amazedwith her smoothness, I stumbled on a short clip of Wade Cox from Edged in Water.
 I bet I've watched the overhead footage 50 times, focusing on the Wade's angle cross course, rope angulation relative to ski angle, Upper body rotation relative to ski angle. edge change locations. I'm kind of a visual learner and this vantage of a great skier brings many of the concepts together. A few thoughtsImportance of keeping handle tight to hips at edge change may have more to do with changing direction of skier. After all it is the swing of the skier that brings him up on the boat and ultimately maximum width in the course. Reduce swing up on boat, reduce width. The skier as a ball of mass going cross course would continue going cross course without imput from ski and/or rope. Rope tension directed to skier center of mass swings skier into arc matching handle path and allow ski to take independent wider path. Since less load on the ski ( rope is doing some of work to change path of skier mass) less load/drag and more speed at the ball. Conversely if arms are let out then the force on the rope is at the shoulders, considerably above skier center of mass, edge change is forced, harsher, cutting short its cast, creating more drag. With narrower path the skier slows sooner, doesn't advance as much on the boat, and finishes turn with less velocity. Also check out (1) Upper Body rotation behind the boat to allowing the ski to cast wide, (2) actual skier cross course angle (3)Upper body counter rotationand forward reach at the ball, (4) Quickness of turn and hookup (5) Skier path vs Line angle (can see zone where line tension in critical and where it is not.) Just good stuff, what do you guys see?