Well, I think a maximum of 2-3 extra names is more than enough. But anyway, it's you who decide how many to put. The only thing you would need to pay attention to is to make sure all the names are sequentially distributed. Taking my previous example, 0x7000 - 0x7003 would be the first, then 0x7004-0x7007 would be the second and so on. That also means you could not use those variables for anything else. While you could teorically have an almost unlimited amount of names, battling needs to be take into account. And then the amount have to decrease because you might want only a few trainer class to have custom names. If you were use too much class values for the custom names, you would have no entries left for the normal trainers. That's also why I think having say 3 extra names is enough.