At the Charmayne James clinic I attended her perfect pocket was the same amount of the barrel all the way around, each time. About 2 foot from the barrel, in, around and out, then onto the next barrel..
You rode almost straight out between barrel one and two,making the turn to the first barrel, stayed about 2 foot all the way around and then straight to next barrel. No cutting into the barrel from the beginning, no sharp angled turns, a smooth motion all the way through. She also had us picking up the inside rein and pushing the outside leg into the horse, not the inside leg pushing the horse out. This would round out his body and make him push with his hindend, less chance of shouldering in.