Conditions in the video are about as easy as they could find. They're going down hill on hard and even 100% smooth snow with not even a pimple sized bump in sight. He even has to take a chairlift to go uphill.
I doubt that you would even need the "Ktrak" for such hard snow.. just downhill knobby tyres would do, I think. I certainly used to ride worse snow on a mountain bike, and could do jumps without snapping bits off.
When I made a ski bob (unpowered) conversion kit for my 20" wheel freestyle bmx I made the rear skid the same shape at the rear as the original rear wheel, so that it would feel similar when landing jumps (touching down rear first). I thought it would slide easier if the middle of the rear skid was actually right underneath me too. Braking could be achieved by lifting the front so the pressure increased on the rear and it would sink.
The front was just a downhill fork replacing the bmx fork so the pivot point for the front skid would be lowered and the suspension would help with the unseen bumps under the snow. I unfortunately didn't have the right springs to make the front skid return to a safe position when I lifted it so I was using bungees which weren't ideal.
I wish I had pics so I wouldn't be trying to explain, but this was before (I had) digital photography.
