I notice the narrowness of the divider between the 2 ports on the flange you are holding. It looks to be almost the same width as the tube thickness. if you use 2 individual collector tubes, how are you going to weld the second collector tube in once the first collector tube is in place? There doesn't look like there is enough room to weld the other in once the first tube is welded in place. Unless the thickness of the divider an illusion, your collector tubes are going to have to fit inside the ports on the flange. Then they will have to be welded from the face side and then smoothed off. But then again, I am not a welder and don't know all the tricks.