P.S. on my previous post about traction on the D series:
To test whether the F series has better traction than the D series, do the following:
Position the machine 1-2" in front of a bollard, wall or other unmovable object (for safety purposes). Jack off the ground one of the tires on the front of the machine and one of the tires on the rear. Attempt to drive the machine forward. If it doesn't move you have a dud, or "D." Reverse the machine and follow the same procedure to check it in reverse.
This is what the factory did for me to determine that the machine is "operating as designed."
Obviously, this design is not what I expected from the performance literature I received prior to purchase. But the real issue is that people should be very careful when operating this machine on any kind of slope. If you get stuck and try to drive yourself out on a slope, like you would with a 4 wheel drive machine, you'll slide downhill and potentially tip over- a rather scary situation to find yourself in.
To mitigate this problem, you might be able to improve traction by adding 1,000 lbs. or so of ballast in the bed. This seems to be what people do in snow country (along with chains and a more aggressive tire).