I use the Hopkins and have them both on the front drivers side corner. One on the front wall and one on the side wall.
I also use a 2' plastic level from Home Depot on the floor just inside the door on most occasions.
This past weekend I was only 1" out side to side so I just left it and everything was fine. It is not that critical that you be "perfectly level".
TT = 2007 Jayco Jay Flight 27bh
TV = 2006 F-350 CC DRW 6.0