Support header sizing for a large garage workbench
As long as it is not a V8 engine block it should do fine. If you hammer anything on the surface, stay near the legs, toward the center you will feel the slight springiness. It will not let anything you are driving with the hammer, like wood chisels for example, will not perform like they should. That particular task may even be a bit unsafe over the span.

Use a cleat on the back edge at the wall so the hinges do no supporting when the top is down as a work surface



I added a sketch to help understand the cleat I wrote about.