if i use wedge formation i make sure that i get the enemy from behind, but right after that i choose close again, it have happen that when i charge spear units i used wedge in head to head charges also, hoping they would brake after a while. Most times it worked, but other times i had to take help from other units to brake the enemys,

attacking soft units as shooters, skirmishers, peasants, urbans i never use wedge