Definitely take your helmet in with you like mentioned. I have the Troy Lee Designs SE4 helmet and the Airbrake XL's are what i just purchased and they fit great. The standard Airbrakes or Airbrake XL's get my vote because the lenses pop out very easily. They also include two sets of lenses when you purchase that model, one for low light and one for bright days.
Agreed. I've run the canopy frames before and had problems with them fogging because they lift off your face when you move because of the helmet. They told me at the Oakley store that Airbrakes were designed for use with helmets and they seem to fit 100 times better. Also the quick change on the lenses is awesome.