Keep in mind that most fish have the majority of their growth in the first few years of life. So any stunting will occur earlier rather than later. Many people buy baby fish figuring when it gets too big for this tank, they'll move it. What the fail to realize is that it's growth is already dangerously stunted by the time it's "too big" for that tank.
But since you already have the eventual larger tank, I think this could work out great. Just be sure to move him sooner rather than later. Like, as soon as he can defend against the triggers.