We have added a new campaign targeting option under General information tab - PrimeSpot. If you choose to buy PrimeSpot only traffic, your campaign will take part in bidding only if the visitor has not seen any other popunders from PopAds within last 60 minutes. Such traffic is higher quality, however it is also more expensive and lower in volume.
It is also possible to split a campaign into two, group them together in order to preserve frequency setting and set different PrimeSpot and bid. This way, you can offer premium bid for PrimeSpot traffic and regular for Non-PrimeSpot.