That porch roof sounds familiar..........My Gable-end porch HAD a bead-board ceiling supported by a very light weight ceiling 'rafters'........spliced 2x4's ran the length of the porch with the "beadboard perpendicular to the house"...........That would never support the swing and passengers.........I could see/check thru an access opening in the attic..........You may need to add your own support........doug