One more opinion on hydration packs-
If you are going on a well supported ride it's my opinion that you don't need the Camelbak. Why carry all that extra weight when you don't have to. If the rest stops are spaced 10 miles apart then 2 bottles should be plenty to get you from one stop to the next. Now, if you don't want to stop that's a different story. But taking 3 minutes off the bike every 10 miles after the first 30 miles is a good idea IMO.