Difference in airfare. L fare so that makes sense.
Very tempting because of the cost savings, but even with the T-3 fare class zeroing out explained in the wiki this may be a bit to risky.
I'll admit I have moved a two-person hub-hub domestic K fare four days, but it was an intense annoyance. Can you afford to fly early if you get stuck? If so, with a reward of $1600, I might be tempted to try.
(I assume this is not international—if it is, that will be very difficult.)