That's up to each state to decide. 5 should still be the minimum because you'll have even more passing than 11-man. 6, 8, and 9 man games are often very high scoring. If you go to 4-man crews the position you lose ii the back judge so you wouldn't have anyone at the goal line on many plays snapped outside the 10. Many states have 5 and 7 man crews now for HS football but we are far from that for two reasons: increased cost and shortage of licensed officials.