I have a lot of i-Pilot river experience at this point. In principle, your i-Pilot can be used to control your speed to maintain the preferred vertical or near presentation while slipping with the current. In practice, I've found that surface currents are simply too irregular, and wind influences too profound, to be able to set one speed and forget it while slipping with the current. I am constantly adjusting speed and direction while slipping, and for that, I need the foot control.