As with every other posting, I understand the problem. How do you slow a boy down without fustrating him? And in my opinion, I think part of the problem lies with the "new" requirements for rank.
When I got my Eagle (1986: I'm not that old!) the requirements included a time in rank, which if I remember correctly, as I was a Scoutmaster before my son entered Cubs, the new rules don't include this very clearly. This, to me is a shame, as boys need the time to learn what Boy Scouts is about.
Now, recently I did meet one Scoutmaster that had a solution to this. His approach was through the Scoutmaster's Conference. This is your chance as Scoutmaster to slow a boy down a little and test him to see if he is really grasping the concepts of the requirements. He would use questions to see that the boy really understands what he's accomplished. Give him questions like what he will face at his Eagle Board: situations that require reactions. It's one thing to know enough to get the requirements signed off, but is he REALLY prepared fo the added responsiblities? That's what this SM and ASMs would try to determine.
If the Scoutmaster felt he wasn't ready, or rather, hadn't sufficiently learned what he needed, He would reccommend the boy to review the requirements and try to understand the importance of them a try again in three months or so.
Considering the value of the Eagle badge, this seemed that only fair way to make sure a boy is getting the most out of Scouting that he can.
Something else to consider, I guess...