You should completely loosen the top engine mounting bolt on top of the head when tightening and torqueing the head nuts. If you leave the top engine mounting bolt tight, that means the head position is fixed. Then that also means you are basically trying to pull the engine up. Since the lower engine mounting bolts are tight, you would be creating uneeded stress on the engine by basically trying to pull it up and apart by tightening the head nuts onto the cylinder studs. That creates unneeded stress. Do it the easy and common sense way by loosening the top engine mounting bolt that is located on the top of the head.