Just got a 2015 f350 long box. came with factory camper package and 18" wheels. looking at getting a set of aftermarket wheels and tires but not sure on wheel size. i have heard that the 18" will have a bigger weight capacity than the 20" but i am also thinking that the 18's would flex more side to side? kinda like the looks of the 20's better as well. anyone hauling with the 20's. or should i stick with the 18's.