I don't know about that airplane specifically but in general there are control horns on the servo and on the control surface with a linkage connecting them.
There are gererally a nummber of holes in each horn. Move the linkage to a hole farther out on the servo or farther in on the control surface to increase the throws.
CAREFULL, make sure you can comfortably fly the airplane before you make any changes and then go one hole at a time.