AFAIK there's only one official skiing pace, which at grandmaster allows me to ski at 6 km/h.
Pressing Shift-r informs you that "You can't run while skiing!"
I just discovered that if I unequip the ski stick, press shift-r, and re-equip the ski stick, I'm able to "ski" at 12 km/h on thigh deep snow.
Whenever I ski/run, the message log shows:
You ski.
You run.
Running while not using skis and ski stick still allows me to run at 12 km/h for a tile or two and then I slow down. This does not make sense to me, especially while running on thigh deep snow without snow shoes.
Disclaimer: I've never skied before, so I may be talking out of my ass.