Well I have checked my cables and there are no stereo cables, I am almost sure that the hi-hat doesn't need a stereo cable.
There are tree chanals in a xlr cable and I think it uses 2 for the hihat and 2 for the clutch function.
I shares the earth channel.
I can not test it anymore, I have a ddrum3 know, but a will try to make a stereo split cable and hopefully a can use the ddrum4 hihat on the ddrum3.
the ddrum3 has to inouts for the hihatm one for the pad and one for the hihat/clutch function.
Like this:
