Pred increases appetite, but does not necessarily put the weight on. It sounds like in Beau's case he is hungry and gaining the weight. My female was on 100mg a day and lost 10 pounds in a week, and that was after eating 5 cups of food a day. She is on 25mg now, the appetite is still there although not as great as it was and she is not losing weight anymore. In my case she is low platelets, so we have to balance the pred with the platelet count, taking into consideration the weight loss/gain. I wish my girl had your boy's problem with gaining the weight because she is way down on the weight.
Hopfully Beau will be able to go lower on the pred and you should see a difference in his appetite. Good luck, I know how frustrating it is to see them so hungry and you can't do anything about it.