LOL! It wounds like you know what you are talking about! :] I bet that you could prove it one way or the other- but the real logic would tell us that if all else is equal and if weight were such an advantage, then in each race the winner should weigh less than the rest of the field in any given race. That should be easy enough to tabulate for the person who wants to take the time to do it.
that should be "sounds" like you know what you are talking about...