Most bitless bridles I see sit too low. Why is this a problem? Read below:
When fitting a bitless bridle it's important to understand that toward the end of the horse's nose, the bone structure becomes very thin and then non-existent, leaving only cartilage. It does not take a vast amount of pressure to damage the cartilage or fracture the end of the nasal bone. For this reason, the noseband of any bitless ( or any halter so to speak ) should sit high on the nose; the general rule is two fingers' width below the protruding cheek bone.
In the picture of the scull you can see the nasal bone and it narrows as it travels towards the lips of the horse.
In the second pictures is my mare wearing a LightRider Bitless Bridle with an illustration of how to fit the bridle by placing two fingers between the noseband and below the prominent cheek bone.
Pictured is my Quarterhorse Little Creek Zena ( Nell ) wearing her Lightrider bittles bridle. Reference for the graphic of the skull is from Google.