Some male goshawks are just wired to carry. I've had them that no matter short of catching something bigger than they are, they will carry or drag. Have you tried letting him fly a little before or during the hunt to get rid of excess energy. I did that for awhile with my last imprint. I'd just let him go rather than bate. He was pretty reliable on the recall but I can't say it worked wonders. I was thinking he had nervous energy and I'd let him take stand and keep hunting with the dog.