My crust tough and leathery

Hi you all,

Using a 275g dough ball  (25%wholemeal/75%bakers wheat) at 72% hydration I shaped a thin pizza base, topped it, baked it at 240C for 16 minutes, it was browned. When it had cooled, I cut it, and it was tougher than usual. If I wanted a softer crust should I shape the base with a thicker edge? And is it important not to bake too long?