They have rain gutter brackets ready to go. They have numerous sizes to choose from. I got one 7' long. Need to verify the height brackets you want and if you use more then 2 brackets on each side ask for the necessary spacers due to a curved gutter line. The brackets are a bit clunky looking but are very stable (no side to side flexing).
The thing that I liked about this rack is the fact that the top of the inner platform rails are flush with the outer perimeter rails. When dragging stuff off the rack in a hurry nothing snags. In an emergency that might catch you by surprise. All of the platform rails and perimeter rails have slots for sliding capture nuts so that one can fasten anything in any configuration (fuel supply brackets, water container straps, awnings, jacks, sand ladders, I had a 6th tire on the top for a while) and change it at any time. Front Runner has a similar system. The one I saw, their the perimeter rails are raised from the platform a bit but probably not an issue for most.
The 8' awning on the drivers side is attached to an articulating arm such that the awning can be rotated and attached to the back of the rack, covering the tailgate kitchen. When mounted to the back of the Pig the 8' wide awning covers from the drivers side of the tailgate to 3' past the passenger side of the tailgate. When the passenger awning is extended at the same time it creates a cover similar to what the "Foxwing" creates. I have a couple of side walls as well as awning extensions which allows me to great an "L" shaped tent enclosure around two sides of the beast.
This rack/awning configuration allows for a number of variations subject to weather conditions. Depending on the positioning of my swine to the weather and sun determines the setup. Awning on passenger side or drives side or both. Awning only over the back kitchen or interfacing with the passenger awning making the "L" cover.
Sorry if this was too long winded. Maybe helpful though.