Replacing with the factory size is certainly the safe route. I have fields that are reached by gravel township roads, many with hills. The orchards in those fields are on varying terrain from flat to steep and everything in between. I also have a trail that leads from the barn to a ridgetop that is so steep, if the fuel tank isn't full, will actually cut out sometimes. I noticed no change in any aspect of the climb except much better traction. I would say that most people who have stepped up one size and even two, noticed zero change in climbing/pulling power and top speed. I would count myself among them. Most important, it is your money, get what you feel comfortable with. If you were operating the RTV on the very edge of its performance envelope, would you notice a few lb/ft of difference? Possibly. But is that where you plan to operate?