How much more would you expand

Hi, I'm including a progress photo of a case I started about two months ago. The chief complaint of the mother of the patient is "I don't like how much his front teeth sticks out". Wits appraisal is -1.5, but he started out with a 5mm overjet. This is a 9 year old patient with a fast erupting permanent dentition. He lost 5 teeth since we started his treatment. I used a mx Schwarz appliance with an anterior labial bow but now his appliance won't fit because of changing dentition. I would like to make another Scwartz appliance for him, activate the labial bow and then place sectional anterior brackets with a powerchain to reduce his overjet once we create enough space. My question is: how much more do I need to expand to create enough room to detorque the mx central and lateral incisors? What are the indications that I've expanded enough? Thank you!