There is no good access point.  I could go the common route of powering off the generator, but the generator rebuilder and I don't like that idea.   Also blocking the manual crank port is a no-go.  So, I'm leaning toward the belt pulley (new pulley), if I identify a good way to mount the pump.  Yes I know this is still problematic in that it's not fully "live".  I don't really find that to be a major problem as long as the hand clutch is working correctly.  Not planning on any separate gearbox.  You can get a pump rated for most any reasonable RPM you want.  I had planned to use a diverter to divert the native pump to a new control platform, but given the difficulties I've had so far getting it to work correctly, I'm leary of that approach, plus a bit more flow capacity would be good.  But nothing's set in stone yet.  I'm still (re-)theorizing.

dfwallis wrote: What would be a proper target GPM size for a supplemental hydraulic pump for a CA (given limited horsepower)?  10GPM?  15GPM? ?  (10GPM ~ 11HP at 2000PSI per one online calculator that I don't really trust)

A couple of years ago my friend bought a (much too large) 3-point hitch backhoe for his little Ferguson tractor; he then purchased a PTO driven pump that was also much too large, it was in the ~17 gpm range or thereabouts (I am too lazy to go look it up for the exact specs).

When he tried to use the backhoe it simply killed the engine on the tractor so he asked me to take a look at it. When he told me how big the pump was I was pretty confident where the problem was. He wound up getting a pump that was just under half the size (again I am too lazy to look it up) and that fixed the problem other than the backhoe is still too big for that little Fergie; it needs a WD45 at minimum.

dfwallis wrote: ...  So, I'm leaning toward the belt pulley (new pulley), if I identify a good way to mount the pump.  Yes I know this is still problematic in that it's not fully "live".  I don't really find that to be a major problem as long as the hand clutch is working correctly...

My late Father-in-law mounted a pump directly-driven on the belt pulley drive of his WD. I see no reason why this couldn't be done on a CA as well. He used a Lovejoy coupler and welded up the pump mount, I think he had to get a small amount of machine shop work done.

only problem with using the PTO and hand clutch is your hands are already busy running the steering wheel and bucket levers.

Anything I do will not mod the tractor itself, just use existing bolt patterns (only exception so far was drilling one hole in the drawbar).  If I decide to do something different in the future, I easily can.  I don't envision a loader, just 3pt devices that need to slide left or right, up or down, open or close, etc.  I'm pretty nimble.  I don't think operations will be problematic or only rarely.  I also don't see anything that needs to operate too awful fast, but I want some spare capacity just in case.  I lean towards a 2000RPM rated 7-10gpm pump run closer to 1000RPM (once I investigate the flow curve vs RPM).  That gives options to speed it up in the future if needed (provided there's the HP to do it).  Also thinking of a clutch mechanism when the supplemental pump isn't needed.

dfwallis wrote: ....  I don't envision a loader, just 3pt devices that need to slide left or right, up or down, open or close, etc.  I...

Hmmm...

This sounds like a perfect application for a 12 Volt snowplow pump.

Looked at a sampling.  Way too tiny flow rate for way too humongous price.  Plus I'd have to add a 12V source of some sort.  I think I like my approach best.  If I decide to change the takeoff source, I can just move the 10GPM pump.  If I need a little higher flow rate than produced at 1000RPM I can change the pulley size and get a little boost (assuming available HP).  The system has to connect to my console of 4 dual acting spools and 2 single acting spools as I've designed it and has to mount conveniently in the rear of the tractor.  A small gear pump fits the criteria best.