Question about mounting tent and awning

So i am trying to figure out what tent and awning i can get to properly mount on top of my truck. From what i understand and remember is that I should not mount a tent or awning or anything to both the rack above the cab as well as the camper shell correct? Reason being that the cab and the bed will both flex differently from each other even though they are on the same frame which would put more stress on the mounting points of the 2 racks if for say the awning was secured to both of the racks. Reason i ask is i know the tent that i want to get will overhang onto the cab a bit. I also am looking at a 270 awning and know that they are longer. I am wondering if mounting it to only the camper shell rack would secure it enough even though it will stretch all the way above the front of the cab.

 

BTT, I have the same question and trying not to start a new thread.