I would try to keep at least eight inches clear.
To adjust the pin box:
1. Hook up to the truck and use the landing gear to set the pin so it is just touching the hitch plate.
2. Remove the bolts from the pin box.
3. Using the landing gear, lower the nose until the next set of holes line up and reinstall the bolts.
No manual lifting of parts involved.
Check the torque after the first couple of hundred miles.
If the nuts are inside the pin box and hard to reach, you can remove them before hooking up and reinstall after unhitching and moving the truck out of the way.
A