my test had to do with no one around my boat catching fish and dropping down 5 feet and watching dogfish attack the ball. I replaced worn zinc's and wire brushed the mounts. a few months later I lost something electrical in the motor (OB) and once that was replaced didn't have much of a problem.

I have since replaced that outboard and am trying to set the boat up again. As I stated I have a personal aversion to braid on the downrigger. so before I got the wire I thought I would check. if isolating works then I will not worry as much.
Eric