Lawrence, can you remove the 5 pm limit for hour? it is very noising :-\
The idea is to limit damage by spammer accounts.
I've now changed it to 10 pm's an hour.
I still consider that to be quite high though.
Is there a specific reason you need such a high number?
If you are trying to reach a larger amount of people, its better to make a post so that people can see it.
Users can subscribe to a thread if they need to be kept updated; thats a better mechanism than PM's.
No larger number of user, but a great number of pm with few users, to develop or improve new features :P