Corner trebs go into slot 1.

src/engine/objects/NPC.java

@@ -1451,6 +1451,11 @@ public class NPC extends AbstractCharacter {
 		else if (!siegeMinionMap.containsValue(2))
 			slot = 2;
 
+		// Corner trebs always are slot 1
+
+		if (this.building.getBlueprint().getBuildingGroup().equals(BuildingGroup.ARTYTOWER))
+			slot = 1;
+
 		siegeMinionMap.put(mob, slot);
 		mob.setInBuildingLoc(this.building, this);