I rode with a different club this morning. We did about thirty miles. There were folks on the ride from 20 - 70. As such the pace was easy...I think for the entire thing we maybe averaged 14
I was amazed actually at the end of the ride that I wasn't even close to tired, I don't even think I sweated with any regularity. I am confident at that pace a century would be a piece of cake. At my normal 60 mile ride pace, I would struggle a lot on a 100 mile.
I say watch your average, since there is no climbing and keep it where this one is in the bag....you can always dialog up the last 30 if your feeling very strong.