L5240 rear hydraulic block question; Is it the last in line?

[rfc143]

In this ancient, but fascinating thread:
http://www.tractorbynet.com/forums/hydraulics/204621-diy-remote-hydraulics-2.html?highlight=30541

BirdBob built a block to replace what looks like a cap with a passthrough from one port to another. This is where Kubota's add on remote valves go.

I believe what BirdBob did was to take the PB port, feed it to a regular all ports blocked/open center manifold and connect the output port of that manifold to (wha I think is) tank.
The existence of the third pipe (#110 in the drawing), suggests that Kubota's valves propagate the Power Beyond Circuit; I think that pipe goes to Tank. It's connected to what I've Labeled "B" in the photo of the rear block. It's currently plugged with a plastic cap.

I have such sandwich valve manifold and would like to do something similar to what Bird Bob did.

So, the general question is:
Can such a typical sandwich valve manifold (that passes oil from the inlet to the outlet through the manifold when all valves are at the center position), be used in a PB system, if it's last in line? That is, can the outlet be plumbed directly to Tank, if nothing else downstream needs oil? Does the PB port at the last thing in line on such systems go to tank?

The questions specific to the L5240 are:
Is the rear 3 pt hitch hydraulic block the last in line? Where does that pass through go? Tank? If so, what is the other port labeled "B"? They can't both be Tank. Finally, Anyone know what "C" is and where it goes?
Any guidance is most appreciated.

 

[Fallon]

The 3pt is usually last in line on the PB loop. It dumps to tank & rarely has a PB out port. Putting the PB out on your valve to the in on the 3pt is the common setup.

 

[rfc143]

Thank you Sir! If I understand correctly what you're suggesting, I'd break (or buy a replacement) the steel line feeding the 3pt block from the loader valve PB port. I believe it's connected at both ends with Banjo fittings. Are compression fittings in the middle of the line acceptable for this?
Also, my valve has only 3/8" in and out ports. Is that likely to cause flow problems to the 3pt hitch operation?

 

[Fallon]

Duno on the fittings, but between the loader & 3pt is where 95% or more of the rear spools get stuck. If the valve & plumbing you are going to install are smaller than your existing plumbing & valves life will suck. I'm sure others will chime in with what GPM a given size hose & fitting will flow. If it's smaller than stock it will cut flow, increase back pressure & cause heating issues causing problems with not only tour new valve, but your loader, 3pt, pump & generally your whole hydraulic system.

 

[rfc143]

Well, I certainly don't want to muck the system up. The pipe from the loader valve to the 3pt valve is about a foot long and appears to be 1/2" tubing. I can plumb the new valve with all 1/2" hose, but there'd be some restriction through the 8" or so of the valve manifold itself. How much, I'm not sure if it'd be a factor, but would prefer not to learn the hard way.