Both, I have an 800mm, 31.8(clamp) on my Rover and love the set-up for the hard pack and road. Alternately, I have an Enduro that's was supposed to be delivered by 1pm today, (right now I'm in garage waiting for truck 30 min late already). I am upgrading the forks to a form of airshocks (undetermined brand yet) and the rear to the dual valve A5 RE, whatever brand that is, that should be on it stock. It would only make sense to upgrade the bars as well.
I have a DPC18 in my hand, I put the bolts in and there is enough flex in the plastic and bite of the bolt to use 35mm Fat bar... Pics can be provided... I want to see the stem Voltbike used stock but, I am mostly likely getting Renthal bars and stem to match...
I am adding 203mm brake rotors also...