From the timers:
"I can adjust the pace to reflect the longer distance, but there's no way to accurately adjust official finish times because there are so many factors involved (and USATF would not accept the times if the gun times were adjusted). Does Chicago use pace or finish time for corral assignments? If it's pace, then there will be no problem.
Flying Pig had a similar issue this year when their course went long due to an major fire on the course, and I did use an adjustment factor when I sent the times to Boston so that they had the official time and the adjusted time for their records, but we never posted the adjusted time. I could do that for Chicago if that would work. In addition, Flying Pig put an "Adjustment Calculator" on their site so people could determine an estimate of their time if the course had been the true marathon distance, but the official time for their race was the time it took to travel the actual distance.
Once Chicago lets us know how they might be willing to handle this we can move forward - and I'm sure we'll be talking."