Each just has the minimum crew of 3. If I ever want to add crew (max of 5 per gun), I am going to do two horse mounted crew with a towing yoke between them to make it appear as if they were horse drawn into position. I think that this would be very strong thematically and would be good for display, even if I never use the extra crew. I WILL be using these though. I think Artillery pieces are greatly under-rated, especially in 6th ed, and for 50 pts a pop, a S6 AP4 ordnance blast isn't bad, especially since it doesn't require LOS. With boots on the ground being the single most important thing in 6th ed. these mortars will effectively wipe average infantry off the table.
Anyway, enjoy the pretty pictures.