Okay, got crossed eyes now from trying to read those, lol. Double check me, the 153 drawing shows 55.9 LPM at the stop valves for the Aux circuit just like the 53 drawing, yes? Then right next to it is the 2nd optional aux circuit stop valves showing 38.9 LPM?
I dug around a bit on the specs and most brochures show the aux circuit for the 153 at the same flow as the 53, BUT the brochure for the US shows on the second page that High Flow Primary Auxiliary Hydraulics 25.6 gal / min is an option. So, it would appear that they're using a 2nd Aux valve section, the last one on the far right in the stack, to give you the flow from the larger gear pump. I have to assume they combine the flow from both valve sections to get the 25 GPM, but it's not shown that way on the drawing that I can see. But then it's pretty hard to follow those tiny lines and read the symbols.
Is your aux control done electrically? Should be able to plumb in an external relief valve and a solenoid diverter valve or a pilot operated one to bring the gear pump flow in at the same time your standard aux valve is activated. Not sure the lines will be big enough to handle the return flow, but if your hammer doesn't mind some back pressure it should be okay. You'll lose swing function while the hammer is activated but I wouldn't think that would be a big problem?
