Is your communication so urgent that you can't wait 20 seconds? I don't see any need to reduce this. It should probably be increased, actually.
The software doesn't support having different restrictions for different membergroups (and it seems difficult to add support for this in the code), or I would lessen the hourly restrictions for most users. I don't want newbies to be able to send too many PMs, though.
20s between posts is a bit annoying, not serious, though. Having to wait an hour to send PMs is a little more serious, especially if there's a backlog.
Not an extremely urgent request. Seems to be a lot of work, so no worries. Will wait until someone fulfills the request for new forum software.