The chair folded up, with its face covers on are 8cm thick. So the spine needs to be more then this to house them comfortabely. I am also still woundering weather to have a floor covering to protect the card.The 5 layers that make up the spine of the pop-up. It needs to be hinged on each side of the spine. In this pic I am using calico sandwiched between the layers of card, creating a membrane hinge.