I figured I'd get mixed responses
The ride is Oct 3 so not much more time to train. They say at the 48 mi rest stop is when you need to decide 68 or 100.
I did think about hills too and asked the club organizing the ride. they said 1600' for the 100, with a 4-5 "noticeable" climbs. On our 50 last week we did 1100', but not too steep.
I'll see how the 60 goes on Saturday. I just need to get my friend to remember to not go all out. What ached the most during our last ride was upper back/shoulders.