The cable wrapping thing on Powerdrives and Terrovas is a major annoyance, but I'm not sure that it has as much to do with the size of the motor/boat as it does poor programming on MK's part. Sucks when you're fishing a spot, not paying much attention and the motor wraps the cables then cancels spot lock. Once you've realized what happened you're way off and get to start over.
One thing that helps is to make sure the boat stops moving completely before you hit spot lock, and approach your spot from straight downwind. I've found that it is most likely to wrap if it has to move the head more than 90*. It should be programmed to only rotate opposite of the last move, but it simply moves whatever direction is nearer to the target heading.
Once I started being more careful about when I hit spot lock, it only tends to wrap when the wind is really variable, or when it's dead calm and the boat tends to move around aimlessly. It definitely works best with a steady breeze.
What bugs me the most, is that mine is smart enough to feel the added drag from twisted cables and cancel spot lock, but it's somehow not smart enough to just not do it in the first place!