Sturdier 3-D Case Redesign

I already have a well-tested 3-D printable case for my tabletop RPG, but two pain points remain before I can release it to the community: the hinged spine needs to flex more smoothly, and the broad faces of each side panel feel too thin for repeated game-night handling... (Budget: $30 - $250 USD, Jobs: 3D CAD, 3D Design, 3D Drafting, 3D Modelling, 3D Print Design, 3D Printing, 3D Rendering, CAD / SolidWorks, Graphic Design, Illustration)