Cheers for that Drooper, I agree with you, I reckon it must be worth about 3-4mph.
I am doing the PFS 110 miler on Sunday and have no one else I know doing it so I am kind of hoping to join in with a reasonable paced group and see how it goes.
I tried the increased cadence thing a week or so back and found my knees to be sore when I finished which is strange as you would expect this when grinding away.