Hide Threads if Post Requirement is not met

Just use User Group Promotions.

Ensure that Registered members do not have the "View thread content", set up a new user group that does have that permission and then promote users who have > 5 posts to that user group.

That would allow them to see the threads in the thread list, but not the actual posts within. Of course you could block access to an entire forum so instead of the "View thread content" it would be the "View node" permission.
 
Top Bottom