The optimum percentage is whatever it takes for your pup to have solid stools. (Not dry, hard to expel bits either) There is no reason to overload your puppy with extra bone at the expense of good nutritious meat/offal/fat.
I do not think my (almost) adult dog gets 10% bone in his diet. But then I don't measure and weigh everything either. I just keep his stool consistent.
Good luck!