I fitted 35mm Vittoria Voyager Hypers to my CX bike today, replacing Scwalbe Centuries of the same size. Before and after fitting them, I did rolling resistance speed tests in Richmond Park. Both sets of tyres infated to 90PSI.
Century Voyager
Small hill 18MPH 18MPH
Long Hill 21MPM 27MPH
It is a damp windy day day so not conclusive.
Worryingly, I had the back wheel step out on the Richmond end roundabout with the new tyres, I was following another cyclist who had had no problem.
Love the look of the Voyages and a total weight loss of 616g is fantastic. I'm hoping the slip was a one off, as I said though - worrying.