You´re right. Bonanno was 26 when he became boss. The feds seems to have overlooked that...

But I´m positive there were other guys elevated to a captain´s rank who was younger than Trucchio throughout Cosa Nostra history. It´s just that we don´t know about them. One guy comes to mind right now...Gaspar DiGregorio (born in 1905) seems to have become a captain when Bonanno took over. So perhaps we should take the feds statement regarding Trucchio with a grain of salt.