Ive noticed this movement in mine as well, I just had to keep telling myself its normal. I could actually look up through the windshield and see the nose of the cab over section moving lol. Its never going to be like you mentioned (as one solid unit though) Because the frame of a truck is made to twist a little bit, Its made to give just a little between bed and cab for going over rough twisty roads. So if your anchored just to the bed alone which is what I recommend your going to notice some of this movement for say as you go over a bumb or rough place in the road because the bed which your anchored to goes over the bumb after the steer tires. I remember when I was a kid and would ride in back of the truck that you could witness this by the gap between the top of bed and back of cab moving, changing/ and would actually pinch your fingers if you held on there. OUCH , Only happened one though. I would think the heavier duty trucks may have less of this movement but that's only a guess. I look at it now as 2 separate units, The cab/ and then the bed section that your mounted which is designed to move and twist a little at times independently from the cab. Just my 2 cents on the subject. And I would think you could actually damage a TC by strapping the nose section to snugly to the front of truck because your making it twist when the frame does. Or trying to make it do this= eventually something's going to give. I don't have any experience with any trucks between a 3/4 ton Dodge and the freightliner I recently purchased. One tons may be a different ball game all together.