I stopped believing people on boxing scene long ago, as they are generally stupid. Just along with that information that they have given you. You can most defently change the ratio through plyometrics or endurance running. You have to be specific about your training though, you train how you play is my favourite moto. More plyo with less endurance and your fast twitch muscles will develop more with your slow twitch fade. Research ATP and how muscles get their energy on how to target fast twitch muscles in your training.