sorry guys...little confusion..the port is 3-4 inches from the hatch...not 3/4 of an inch...my bad....and could you explain about the bracing a little more maybe?...well the box is moving enough to vibrate around and will move itself...but i cant tell if that is because my bottom is flexing so much so where it moves the box or if my spare tire cover is moving and causing the box to move
that port piece is probably shaking bad, you need to brace it either inside the port, or inside the box. and its pretty close to the back of the inside of the box
it would make it heavier and if it is not on a perfectly level surface already, the added stiffness would help with bottom flex. That bottom flex could be the source of your problems. Thats really a pretty good idea, I think.