One thing you are probably not doing, is having a separate mobile version of the site, which would be the most profitable part. You need to work hand in hand with programs like
Bitter Strawberry, and
Sex Goes Mobile, in order to make money in this business, these days. Mobile popunders from
Plugrush, are essential part of the equation too.
Other ad networks to consider are
First Mobile Cash, and
VPS Mobile, and they may turn out to be even more beneficial for your site, but that depends on the niche used.