Noticed that you are trying to balance the page, but on my screen anyway, sometimes the right ads are Not Visible (like right now), sometimes they are cut in half vertically, sometimes they are fully there....but it squeezes the forum topics, and you have a lot of dead green space on both sides once you get past the top, where the ads are.

Just my take on it, but it is more visibly appealing to keep the green area on one side rather than both.

In fairness, you could juggle the sponsors weekly/monthly, so everybody can get a shot at top of the column.