If you have the original text file for the hack, I could put it on my To Do list for porting to Threads 7 (attach it here). If not, I could probably rewrite it when I get a chance.
Hack Notes:
Starting Point - /scripts/addpost.inc.php, Line 566 (Beta 3 Scripts)
CP Integration or hijack the Manage Forum Dropdown to accomplish this
If there was an API that existed post-addpost, you this could be accomplished without modifying the base code.