I recently picked up a new to me 950 cat for the farm and found a hay squeeze attachment at an auction to possibly try for. Before I get to invested was wondering if and how much of a pain adding a third valve might be. Trying to decide if the project is worth taking on or not.
Using real Cat parts for a third valve would probably cost more than the machine is worth, even used parts. I have seen an aftermarket hydraulic pump( much like used to be used for hydraulics on low rider cars) with the tank attached, and a single valve mounted next to the operator seat, and used to control a quick tach on a mid 1970's 950 loader This might be an affordable solution for you, or then again it may be a hairbrained idea that never should have happened
you can plumb in a diverter valve but then you will only be able to use that one function at a time trying to find a control valve with a 3rd section will be tough
I found the power beyond port on my old 922 loader and just connected a hose to that, went into the hydraulic tank and blanked off the existing oil return and then installed a third external valve with the oil returning to the tank via another port. You just have to make sure the oil returning to the tank must be blow the reservoir oil level and with a bit of a distributor (pipe with the end blanked off and holes drilled along it around the circumference) to distribute the hot return oil so it mixes with the cooler reservoir oil.