When I used the Medela Swing, I pumped on the highest setting.
With the Lactina, it was about 65 or 70%. Initially, I used 90% but it gave me blisters.
With the Medela Double Pump (I think that model is similar to a PISA?), I can only pump on 40% power without it being uncomfortable.
What about you? I know they say that a higher setting doesn't necessarily mean more milk, but it does make me wonder.