Thank you for sharing your feedback on the Cargo Carrier you purchased. We are sorry you found it difficult to assemble. We are always trying to make our directions and manuals as user-friendly as possible so we will definitely revisit this one to see if we can make improvements. The 1.5 mount does only have a rating of up to 300 lbs so if you were near that weight limit, this could be why you had some movement in the frame. If you can, we would suggest going to the 2" bar which would up your cargo weight capacity to 500 lbs and eliminate any further shifting in the carrier's frame. If we can be of further assistance, you're welcome to call us @ 800-489-1581 (Mon-Fri, 8am-5pm) Thank you for choosing Masterbuilt @ your local Home Depot!