Dialog box size.

How do I change dialog box size? I'm talking about the tutorial text boxes which pop-up from time to time when you start new game. I changed it's mesh itself, but it didn't help. So I think it has something to do with game_variables.txt. I tried to change some most probable lines there, but nothing helped. Well, I think I'll find the lines I need eventually (if they're there), but it's really a lot of them. So is it known which lines are responsible for dialog box size?