Brumby,
I'm not much of a weights man to be honest. I believe that a fit, fresh horse in a suitable race is a far better betting proposition than a well weighted horse in an ordinary race scenario.
It is quite common to see a horse come out of a high quality race and fail in ordinary company. The weights often don't play a part in my book; moreso the horse is flat from an over exertion against high quality opposition.
Prosecution at yesterday a perfect example. Ran a bottler at Group Two behind Arlington Road then ran second last in a hackers race at Warrnambool. The big run took it out of him.
Conversely, the drop in class can result in an easy victory despite huge weights. It's up to the punter to analyse each horse on its merits.
Strong, fit, keen 500kg beasts will not be concerned about the difference between 55 kgs and 57kgs. Rather than carrying 11% of its own bodyweight its carrying 11.4%. It's like a supremely fit human being asked to carry 320 grams extra .. negligable.