A lightweight flame-resistant composite panel is provided including a body portion and a side portion folded over the body portion. The side portion includes a channel segment adjacent to the body portion, and an overlapping segment adjacent to the channel segment. One or more panel apertures are located in the body portion and the channel segment for receiving bolts through the side of the panel. An edge reinforcement insert can be inserted underneath the channel segment in a channel defined by the folded side portion along an edge of the body portion. The edge reinforcement insert includes one or more insert apertures for receiving the one or more bolts through the panel, thereby increasing the bolt bearing strength of the panel along its edge. The edge reinforcement insert may comprise an elongated strip, a plurality of separated tabs, or an end cap, or may alternatively be contained within the panel.