Abandon thoughts that he's not "strong" or "energetic" enough. Both of you, especially him. If there's one thing that's surprised and helped us a lot, it's just how full of determination my tulpa is. He might not seem that way to most of you, but man, when he starts doing something, he does it. Failure isn't an option, he'll just keep trying until he does it. And what do you know, he often does it. How? Just by doing it, because he wanted to. It's the mind, there's no magical buttons you can press to make stuff happen. It's just willpower.
Your mind plays a big part in, well, all these mind things. That's what all this is about. Your mind and how much you can shape it youself by just willing it to happen. Don't think you can't do it, know you can do it. You might want to take a look at how positive affirmations really do affect your mind.
Maybe forcing more would help you to feel it better? Do some mental workout to get those mental muscles in shape. Maybe I shouldn't mention that it probably is just symbolism, but if symbolism helps you to think you can really do it, then it's good symbolism in my eyes. If there really is a thing about tuppers not being "strong" enough because they are too young or something, then forcing more should fix that, too.