If your cardboard mockup wobbles, your final build will too
I built a shelving unit prototype last month and skipped bracing the back panel because it was just cardboard, then the real thing twisted 2 degrees out of square on install. Cardboard shows weak joints and flex points way before wood or metal does, so fix it in the mockup or you're just moving the problem. Anyone else had a flimsy prototype that predicted a bigger failure?