I have a 3/4" bed mat (Ford) on my unlined bed. My Northstar sits on a 2X3" frame to clear the truck roof and lights. I use Torklift fast guns,tight,but not so tight that they will damage the camper. We've done three cross country trips,including off road travel,and have never had the camper move more than a fraction of an inch.
You don't have to off load to adjust your camper. Using the legs individually,it is possible to adjust the position of the camper. I would recommend that you block the front of the camper to prevent excessive movement before you make any adjustments. Then tighten your tie downs,just not too tight.