So you have a separate lever for controlling the grapple open/close instead of the buttons on the loader joystick, or did you rig something else to work?
I use the installed control valves for the remotes. It was pretty simple to run hoses with quick connects to the loader mount arm that allows me to disconnect the lines when I remove the loader. On previous tractors I ran hoses up the loader arms, but since the dealer installed the lines on this one for the third function I used those instead. It's really no different than the control of the hydraulic top link.
I guess it doesn't bother folks to have hydraulics operating at full tilt, but it just goes against my grain. I much prefer slow and smooth.
One other thing I really disliked about the third function valve was where Kubota mounts them; on the underside exposed to brush etc. I ended up making a skid plate to protect the valve body which IMO should have been part of the valve install to begin with.