I am using Xicoy and jettronics valves, so I do not need UP products. I have not had any problems earlier with combined systems and I do not expext them now either.

Usually the leak is from air cylinder or supply intake..

Personally I do not like using a slider for brakes. I have set up a 3 way switch with parking brake at low position and springloaded up position is at different value which gives lower breaking power to keep wheels from locking.
Slider just does not feel ok to me for using. Now, if we can always get a constant pressure for brakes, its easy to set up brakes not locking with Xicoy valve as it has a pulsing option.

And of course I have mixed channels so it prohibits brake and steering when gear up selected. Also gear up selection is prohibited when engine switch is off, just to prevent accidental retraction while servicing the plane.