more upright position? Also stronger riders. I have ridden a 1200k with a hydration pack. I wouldn't switch now, a month before the ride, because I haven't been using one. Wouldn't be prudent. In any event, the track record of hydration packs on PBP isn't good. In 2007, about half of the riders that wore hydration packs and responded to the Bike Quarterly survey didn't finish
http://postrestant.co.uk/wp-content/...quipsurvey.pdf
Shermer's neck is probably muscle fatigue from holding your head up. It usually affects older riders that probably have lower core strength. I have never heard of a person riding an MTB getting it, but I suppose anything is possible. It's more of a RAAM/randonneuring issue. I even saw a recumbent rider with a case of reverse Shermer's neck after PBP. Either way, it's miserable.
But anyway, in addition to showing the layout of the controls, I was hoping to get information from people that have ridden in France as to the availability of water and other supplies, not really discussing methods of carrying large quantities of water. You can get water every 60 miles or less, so unless it's really hot, I don't think a hydration pack is needed. If I was riding TABR or some other ride where water can sometimes be hard to get, I would probably use mine.