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Perhaps this won't work for you....who knows. But a number of us tried this a while back after someone (apologies can't remember who started the thread) suggested removing CPM had significantly increased their revenue. Others reported that CPM worked well for them. I guess it depends on your niche, and CTR on normal adverts. I suspect if you have a high CTR then removing CPM would be a good move.
Beware the CPM myths.