Kubota M6040 Hydraulics Schematic

[jwr2012]

Does anyone have a schematic for the hydraulic system on a Kubota M6040? We're trying to hook up a snow plow in place of the front-end loader (FEL), but would like to still use the existing joystick, and the 4-hose quick disconnect (QD) systems. But as is often the case, it tain't as simple as it seems.
We need one pair of lines for plow up/down control, which works fine (no problem at all).
But for side-to-side, the snow plow has two one-way hydraulic actuators, which each have only one pressure side (no "down" pressure on the backside of the piston to retract the actuator, only the force of the other piston pushing the blade out, which retracts the unpressurized actuator).
In testing the four-hose quick-disconnect, up/down is very straight forward: one side pressurizes, while the other is the return line, and then they reverse roles for down command. But for bucket curl-up and bucket curl down (joystick LEFT and joystick RIGHT) we get both QD's pressurized for joystick left, but only one line pressurizes for joystick right.
Is there some sort of shuttle valve and/or check valve on the loader itself, to allow the unpressurized hydraulic fluid to move from the actuators? Is there some other control valve involved?
Any advice or insight would be greatly appreciated.

 

[jwr2012]

More "clues" to the curling culprit.
We decided to get away from the two single-action hydraulic actuators on the snow plow (to push left, or push right), and tried to use one, dual-action acutuator.
So when we hook up a dual-action hydraulic actuator to the "bucket curl" lines, guess what? We get it to extend when the joystick is left (CURL UP) and it extends even further when the joystick is right (CURL DOWN), but it never retracts in that position. So we reversed the hydraulic lines, just for Sh1ts and giggles, and it works just fine extending and retracting.
The best we can figure out is that the curling is controlled on the CURL DOWN, to prevent the weight of the bucket and the weight of the load from just dropping the bucket in freefall (if the return hydraulic line were allowed to free-flow the fluid back to the resevoir). It seems that 2750psi of pressure is put on the main piston to push the bucket down, which overcomes the 2750psi on the perimeter side of the actuator (which pushes the bucket to curl up). It's weird, but that's the best we can figure.
Anyone have any ideas/experience along these lines?