Forget about the FB41 for now. The most important part is understanding your system.
dPressure/dt=PressureRate=BulkModulusOfOil*Flow(t)/VolumeOfOilUnderCompression
The BulkModulusOfOil is about 200,000 psi.
Flow(t)=RatedFlow*Voltage(t)/10*sqrt((SupplyPressure-Pressure)/(2*RatedPressure))
Voltage(t) = Kp*(SetPointPressure-Pressure)
If there is no leakage in the system, and most test systems don't leak, then pressure is an integrating process. You can probably get by with just a P gain that is easy enough to do without the FB41. The problem is how fast will the pressure change each scan or 10 milliseconds. If the volume of oil being compressed is large then the rate of change will not be high. However, if you are testing short pieces of hose the volume of oil will be high and the pressure rates may be too fast for the PLC to handle.