Here's a picture of what lurks in the nightmares of every half-guard player: the sit-out.
Xande is a little ambivalent about whether he wants to hook the head with the outside arm or throw his upperbody over; he does both while working to pass the half-guard in this ADCC match. The key thing I want to focus on are his hip and leg positioning. What is the best way to control his hips, and then exploit his position for the sweep?