What does everyone think about the electric trolling motors that mount directly above the prop on your main engine? Seems that the real plus is that you can steer using the main steering, but at the same time, isn't it a big negative that you cant use this type unit shallow ( e.g., sometimes you need to get shallow with a trolling motor), but I wouldn't think you could really do that with this type of mounting? Thoughts ?? Anyone use these trollers?