I'm training for Chicago October 8th. I'm shooting for a mid 2:20's time. My half PR is in the 1:09's and my training so far this cycle has been going decently well, so I'd like to take a shot at breaking my half PR. However there isn't really any good half's i can find between now and full at Chicago. The Philly half is on Septmber 17th. Is that enough time between making an attempt at my half PR and the full? Or is that just foolish