The combination of hills and a headwind is what burned me in the Pelotonia last year. There were a few times I actually was being blown backward while riding uphill. It slowed me to 8mph even on the flat sections when I normally ride 14-16. Completely demoralizing. I was drafting off total strangers at one point. Fortunately they didn't seem to know what I was doing or didn't care. I think they just thought I was being nosy and wanted to hear their conversation. It totally sucked!