I have been playing with my VBM Domobar Super Double Boiler for about a year now. When I first received it, the OPV was set to 11.4 bar indicated. Within a few days, I dug right in and adjusted the OPV to 10 indicated (estimating 9 bars in the PF). I also wrote to the dealer from whom I bought the machine, asking why the OPV was set so high, if the general consensus was that the ideal pressure is around 9 bars. A week later, I received a message forwarded from a VBM engineer in Italy, who said that "11-12 is the standard in Europe."
Over the months, I started wondering whether I should not have played with it at the factory-set pressure a bit longer before adjusting it. Finally, a few weeks ago, I went back in to reset the pressure. I worked on a cold machine, with both boilers off, setting it to 11.5 bar. When I began pulling shots, the pressure went up to 12 bars. I did notice the flavors to be on the bitter side. Today, I went back and set it to 10.9 bar on a fully heated machine. What are your experiences?