I just purchased a Cervelo P3 aluminum and my HED Jet 6s fit in the front, but barely fit in the rear...I'm talking maybe 2mm on each side of the chain stays. I haven't ridden it outside with the rear wheel yet. Not sure if thats enough clearance, but I though I'd make you aware of it. My HED's measure 27.4mm with tires.

Wow.....too close for comfort for me. THANK YOU for posting! If you end up giving it a spin outside, please post results.