From that thread, by Synthex:
"Yes, you can use Roland FD8 for the hihat controller.
You need to plug it like that :
HiHat Power Source <-----> A fixed resistor (5k to 25k) <-----> HiHat Input <-----> Roland FD8 Controller <-----> GND"
Yes fd8 is only a pedal with a film variable resistor and a rubber finger. But it works well and right out of the box...
I soldered the resistor on the input jack of MD (follow the scheme from Synthex)
I don't use alternate input, i use the main one.
Try with an exp1 or exp2 curve.