You have mentioned that your tractors have Pressure Control fitted. The latest photos posted are of a tractor without PC. No PC body, pipe or diaphragm are shown. The two attached pages from the MF Hydraulic Adjustment manual show the components and the setting barrel 'A'.
I have deliberately printed the first picture upside down to make it easier to see the components. This was originally taken when the hyd cover was upside down. The position of the barrel when the quadrant lever is fully lowered in the PC quadrant will give initial maximum pressure. The second image shows final adjustment being made. On PC tractors this is the relief valve so the barrel should be adjusted to the correct pressure for the tractor. Non-PC tractors have a conventional relief valve screwed into the pump body.