Last Long Run, big negative split

Tonight was my last long run.  I had to work today, so I didn't get to start the run until about 7 pm.  When I got home, it was raining with lightning, thunder, and hail.  Luckily, the weather passed and I was able to get out for my run.  It was super humid, but race day will likely be similar.  I decided to employ a similar tactic to race day.  I want to take the first half at no faster than 9 min miles and then see how I feel on the second half.  I'm basing this on how I felt at IMAZ.  When the calf cramp finally subsided around mile 20, I dropped into the low 9s.  I figure if I can keep my run under control for the first half, I might just be able to pick it up a little and negative split.  Anyway, I went out and ran right at 9 min miles for the first 11 miles and then ran whatever felt good for the second 11.  I settled in and put it on cruise control, which ended up being around 7:50s for the last 11 miles. I felt strong the whole time and posted almost a 12 minute negative split.  I realize I won't come anywhere near that on race day, but even if I do 1/6th of that, I'll be having a great race.