I would, preferably ,use a flat bar shoe and add the wedge pad to that. This does two things, first, it gives the support needed, and the wedging to help the navicular problem. Second, the bonus is you have padding for the sore part of the hoof. This is important for a barrel horse due to concussion sensitivity and creates a situation of being able to dissipate the concussion as well. When you do the rocker, make your trim VERY conservative, back the toe 2/3 the way to the white line and then rasp in your rocker and fit your shoe. Barrel horses with that configuration a-fixed to there foot, greatly benefit also from clips to secure all that you have added to the foot. However, to some degree, the "rocker" is a clip.

 

Good luck,

David

 

P.S. round or bevel all the ground surface of the shoe to enhance break over in omni directions for the barrel horse, as well as softening the landing/concussion  of the foot, in that the shoe is not as flat.   DH