Under what condition is a follower's (Ma'mum) prayer invalidated regarding his physical alignment with the Imam?

Rulings on Following the Imam (الإقتداء) and Row Formations

• If his toes extend beyond the Imam's toes.
• If his physical heel ('Aqib) extends forward beyond the heel of the Imam.
• If he stands to the left of the Imam.
• If he stands exactly level with the Imam.