Ok I've noticed a bug in this hack which means it does not work.
I have a fix for it, it requires modifying index.php and member.php (you only need to modify member.php if you have the "percentage of total posts" hack installed, and do not worry, even if you have pruned and the counters have reduced on forumhome, they will shoot back up
I don't have enough time to post the fix right now, but I'll post it in 30-60 mins.