I wouldn’t worry about the stress of adding a jack plate, if you keep the setback to a minimum, such as 4″ or 6″. While more setback might gain a slight bit of speed, it also could come with some downsides, such as, transom stress, an increased tendency for the boat to porpoise, and also your boats trailer weighting balance on the trailer was positioned with no setback in mind, and the more the engine is set back, the more your trailer will want to wag if you make a quick movement with the steering wheel. If your winch stand is movable, you could always move it forward a couple of inches to better balance it out. I really don’t think transom stress is the real concern, heck the new Skeeters come with 12″ of setback, but I would think that their position on the trailer is set accordingly.