I'm helping a friend install a swamp cooler in AZ. We're thinking of placing it on a mini-deck built on 2 4x4s coming through the side attic wall at the gable end. We'll secure the 4x4s to cross members nailed/screwed to the truss framing in the attic. Does this sound like a good approach? He's attaching it to an engineered distribution system of ducts in the attic. Any advice?