Both the loader and BH should have a relief valve. The relief valve is usually close to the input port of the valve. You can build your self a QD plug in gage, or mount the gage at the IN port of the loader valve, using a tee, and leave it there for trouble shooting, etc. Set the loader and BH for the same pressure unless there is a lower limit for the BH. You also need to know the pump pressure limits, and keep it about 50 to 100 psi below that.