I would think the attachment would have a pressure relief that would bypass excess pressure back to the return side other than turning the system pressure down you'd have to rig up a regulator of sortsSince other fluids (water, air, welding gasses) can be regulated it stands to reason that hydraulics can be as well.
Check out what the fine folks at Parker hydraulics have in that category. Alternately, you might contact the manufacturer of the saw and see if they have any recommendations as I'm sure they've run into this issue before.