What are you doing? Is the SEO so important to your forum? Did you try to talk to your regulars- they might be unaware of the problem.
I still cringe if I have to read trough a longer thread/topic finding out that it already was closed or totally misplaced by category and title.
In the end the rigor of the answer of the owner reduced my activity in the forum quite a bit in the last six month. Do not forget regular contributors might be what is a worth you can not easily replace