Yeah, most recommend a non-carbon post if you're going to use a seatpost-clamp on rack. I can get the ten essentials in my jersey pockets and underseat bag. If that's not enough for you, Jandd also makes a massive underseat bag. (originally for full-susp. mtn bikers before hydration packs got successful). Of course, there are also tons of time-tested underseat-bags by brooks, berthound, etc.