Notice the very aggresive position in this kipping pull-up. It demonstrates the need to let the torso move back and forth through the shoulders. The shoulders and arms provide the "anchor" in which the body moves around. We see many people try to follow this "pillar" by keeping the head and torso in line. This will sap the energy from the kip. Remember movement equals energy and energy is needed for the kipping movement. Move the head and chest forward through the shoulders and then backward as the legs move forward. Obviously shoulder flexibility will play a critical role. During your warm-up practice the kip without actually trying to pull.
Wednesday Strength/Skill work: OH press 5 X 5. As a group, follow each set with 2 sets of 30/30 jump squats for max reps. Do as many reps as possible in 30 seconds then rest 30 seconds. The idea here is to work on max power and transition time (dip and drive quickly).