While the trailer has a regulator to protect the plumbing in the trailer it is a good idea to use a regulator on the input end of you hose to protect the hose. That regulator should be set in the 45 psi range.
I have never been able to see any useful purpose for the Camco regulator. At best it may be a volume regulator but it can not regulate pressure. A pressure regulator has to have a method of controlling pressure. That can only be done by stopping off the source pressure. Pressure regulators do this with a diaphragm valve and a spring. When the force on the diaphragm from the trailers internal pressure and that of the spring is equal to or greater than the city force the flow is stopped by closing the diaphragm valve and will remain closed till the trailer pressure drop below the set point. As long as you can see through or blow through the Camco it is not a regulator
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles