I checked your install instructions, and I think it won't be easily done with the way you set it up. For it to be forum specific, it'd have to be coded into the newthread.php and newreply.php (or whatever) files, something like
PHP Code:
if forumid=xx
display("NP")
(but then in correct PHP coding and all - I'm still a PHP n00b, lol)
But you added the entry fields and all to the templates, not to the pages. This way, I don't know if such PHP coding would work...
We need FireFly or so in here