With aid station at every 10miles in a ironman... there is only need for one or two bottle really.. so the p4 aero bottle and put another one if you want on the aerobar horizontal between your arms......that bottle can be exchange at every aid station. So really, if someone as a problem with hydratation on a p4 during a ironman, i would recommend him to get a good coach and learn the art of nutrition during a ironman.
look at many of the pro racing with one bottle only....they are a good exemple of how to do it......
Personaly, i see the p4 as the ideal ironman bike...... 2000cal in the aero bottle, and gatorade or water bottle between my arms as i go to aid station...
Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching Instargram