Cbeck or have somebody on the ground check if you ride with your heels lower than your toes. English stirrups are designed so that if your feet are not correctly angles, and you are stretching your legs into the stirrups, your feet will not stay in the correct position. “Heals down” is still correct, however, what riders are often not told is that pushing down does not work. Stretching into the stirrups does. Not sure of the anatomical reasons for this, but stretching works, pushing down does not.