Only question that comes to mind is he stated they test the system at 90psi, then why would he say set the pressure incoming at 45psi. I personally use max of 60psi as I like water pressure when showering.
I found out thru a web page that the pressure regulators that you CAN NOT set, they are factory set, restrict water flow period.
I tried both factory set and the adjustable and noticed a significant increase in pressure with the adjustable regulator set at the same pressure.
Again, I use max of 60 psi with a water softener and all works well!
Happy Glamping!!