Yanmar VIO pressure relief for PTO valve

So the Yanmar vio70 has a fairly kickass hydraulic system there's a PTO valve that on this machine was set up to run the tilt bucket. I opted to put a thumb on the stick as that'll be something I can use a lot of! Anyway after a small mishap, I went looking on how to reduce the pressure on this PTO circuit. There are quarter turn valves on the boom that are great when changing hoses etc, what a nice feature! On the valve for this function, there seem to be two kinds of inserts, the one I have uses a 6mm allen head bolt, 12mm locknut and when you reduce the tension on the bolt, it must just open a valve bypass, I can use it to limit the max pressure and allow the thumb to collapse back under bucket pressure but it ends up with 0 holding pressure. The parts book calls out two valve inserts 172422-74900 Valve Assy, Relief 172146-74720 Valve Assy, Shutoff I'm guessing I have the shutoff valves Anyone have a good picture of a relief valve? loosening the allen screw drops the pressure and there looks like a small short piston inside that can get pushed back. Logic says the relief would have a screw and a spring in there to adjust the tension versus adjusting the clearance. Calculating area and pressure and spring tension could be done but finding the correct insert would be better.