Dang, I forgot a 5th wheel commandment:

[Mark N.]

The one that says "Ye shall nevermore pull forward from the hitch until thou hast dropped the tailgate."
It isn't severe. The tailgate still closes and latches, but it doesn't close flush. The latch got pushed about 1/2" out of its hole.
Crap. I wonder how much this will cost to get fixed/replaced. My truck has less than 4,000 miles on it. The first one always hurts the worst, huh?
But the Montana was unscathed! (As one would expect)