Methods of manufacturing structural panels for use in manufacturing aircraft fuselages and other structures are disclosed herein. In one embodiment, a structural panel configured in accordance with the invention includes a skin and at least first and second stiffeners. The first stiffener can have a first flange portion mated to the skin and a first raised portion projecting away from the skin. The second stiffener can have a second flange portion mated to the skin and a second raised portion projecting away from the skin. At least one of the first flange portion of the first stiffener and the second flange portion of the second stiffener can extend toward the other of the first flange portion and the second flange portion to form an at least approximately continuous support surface to which a frame can be attached.