Shorter cooling flushes are not the be all and end all....
Manufacturers usually get it pretty right. By reducing your boiler pressure (esp to such a low figure) you run the risk of negating the machines ability to recover during successive shots...ie your successive shot temps will get cooler and cooler as the machine will be slow or unable to recover, thereby adversely affecting your "temperature stability" at the low end, and making it less able to cope with groups such as at dinner parties etc. where coffees are to be made one after the other. And your coffees will be sour.
Certainly all of this depends on the brand and model of machine, some are better than others.
Remember, HX machines are designed to be used in commercial situations and with continuous use.
In the home situation you dont get the continuous use side of it, and this is complicated by some owners wanting to leave their machines on all the time. This results in overheating....so they want to cool them down. Cooling down adversely affects the machines ability for continuous use......ergo, you have one effect working against another. *
There is a compromise, and the manufacturers of good quality semi commercial espresso machines have usually already worked it out for you through their internal design.
If you fiddle further you run the risk of upsetting the balance, especially by making such a large reduction in boiler pressure and placing it well below design standard.
Also, once you start reading temperatures with your thermocouple, and you see normal variations that you can get with a quality HX machine that is working quite normally and as it should, it may set you off on a tangent trying to fix something that aint broke.
Suggest setting boiler pressure back to the range of 0.9 to 1 bar, leaving it at that, doing appropriate cooling flushes as required dependent on how long the machine is left idle between sessions, and enjoying your machine and coffee.
very first CS site sponsor.