Hello,
I've haven't been through this yet, but the only thing I can see is maybe trying to increase his awake time before his 2nd nap? I've read other places on the boards that their lo's seem to be able to handle more A time in the afternoon. It could be the case since it has been harder to get him down and they also say that 45 min. naps can mean not enough A time.
Otherwise I know there are some that go down to 1 nap as early as 11 mo, but I think I'd experiment with his A time first.
Amy