Another great run! What is your goal time, again, for the Half?? Wasn't it around 8:15 pace?? You just ran an 8:09 pace 9-miler with significant pace increase at the end and now a 7:28 pace 5.4 miler, both in the middle of a training week without tapering. Both of those runs indicate a faster 1/2-M race... I think you have built up some serious flexibility on your goal time!
Have you seen this calculator??
http://www.runworks.com/calculator.html
It was mentioned in a thread on Runner's World. It allows you to estimate effects on pace based on terrain, headwinds, etc. It's pretty amazing to see the predicted effects of even a 10 mph headwind on pace.
I have to admit, though, I used the calculator for adjusting time based on uphills and downhills and found that it gave some pretty outlandish numbers and really overestimated the impact of uphills.