The set up I use as can been seen in my profile pic, enables me to lift large round bales to full height with no issues at all. My rear tires are filled and, normally, I don't have anything on the back when I do so.
However, on anything other than flat ground, it does not take much to get my bum hole squeaking when lifting bales up so that there is space between the bottom of the bale and the top of the hood on the tractor. A couple of our feeders are in locations where this is required. Generally, during transit, I keep the bales as low as possible.