The bandied around numbers here make me doubt my figures even more
It might be overreading a little. Maybe 10-15%.
Dont be put off by the actual numbers though. It's the same reason that guys in the weight lifting threads will talk about weight in relation to their bodyweight (they might be aiming for a 1.5*bodyweight squat, or something).
Here is a random example I found:
TrainingPeaks power data from stage9 of TdF 2012. It's a TT and just under an hour long, so a great indication of FTP.
Janez Brajkovic (page 1) is the only one i'm looking at because it seems the others are probably not trying 100%. (Brajkovic was a good GC contender and finished the tour 9th overall, so was definitely trying).
His FTP is around 358w.
I'm going to do an FTP test on wednesday and I expect to be close to that. It doesnt mean I could keep up with him though.
He's about 20kg less than me, so he's doing 5.6w/kg and i'll be lucky to get 4.5