Tubas aren't that big. You've probably seen the big tubas that they have in parades or other special occasions like football; that they have wrapped around they're shoulder. That's another type of Tuba called the "Sousaphone." I'm 13 and my mouth is above the mouthpiece. Also, it's the biggest of all the tubas at my school and I think it's pretty big. Lizard Dude, you're in your late teens I believe, right. Well, I think he could handle it, Maestro. If he's tall enough to be over the mouthpeice than there you go, ready to play. It's not too hard to play either. 4 valves vs. 88 keys. 4 valves vs. some hard to reach positions for the trombone. Wow, that's hard; 4 valves. The tubas also have the most range in the Bass Clef class. I've played a note about 7 or 8 leseuir (I think I spelled that right) lines below the staff. One of my highest notes was about 5 lines above the staff. So that tells you how large the range is. They used the one and only tuba for the base in SSBM and the tuba sounds awesome at Peach's Castle. Why don't you listen to it one time. I just printed the Mario theme for the tuba, in fact. Now, I'm not saying that you should be a tuba maniac. I'm just stating some facts about it. But it would be cool to play it one time in your life. BTW, (useless info,) My Bach mouthpeice costed around 82-90 dollars.
My Quote: "Yesterday, when I''m smaller.... I wanna fight that Mario the day before yesterday."