Montresor - 7:55 pm on Apr 12, 2013 (gmt 0)
It's a forum with 2400 pages.
You consider that big? Forums are notoriously hard to monetize. Advertisers generally look down on those visitors. So...
1. you have an upward climb no matter what you try.
2. you face absolute rock bottom of the barrel CPM
3. forums produce the absolute lowest CTR possible because forums are poor earners.
Manually editing ad code for even a substantial portion would take more time than available.
More time than flipping burgers?