Not sure if this is the best way but change the amount you will bid with google ppc until impressions and clicks reach a maximum. So for example $5 a bid gets 100 clicks and 1000 impressions (according to googles estimator) and 6$ gets 150 clicks and 1500 impressions and $7 gets 151 clicks and 1510 impressions then it looks like a $6 bid will give you #1 spot. Hope that made sense.