Hunters on the flat should carry something slighty less than a training level frame on a very light passive contact, with a lot of movement from the shoulder. They should move in a connected manner, rather than a dresasge frame with a lot of contact.
Your horse is lovely, but he doesn't scream hunter to me, more dressage horse.
Compare the head and neck carriage, the contact and the movement out from the shoulder to the horse in the photo. You do see horses pin in Hunter Under Saddle classes with their noses a little closer to vertical and a little more frame, but the movement, contact and attitude on this horse are all very close to what judges look for.