I know that a big buck can rub a little tree but a little buck can't rub a big tree.
I respectfullt disagree with this statement. The height of the rud is a better indication IMO then the size of the tree.
I was wondering if the size of the scrape can determine the size of the buck.
Not neccessarily. PL is right on as far as the scrapes. The best bet of judging a deer size by a scrape is if you can see a track left behind by the animal and then that's not for certain either but can give you a general idea of what's been through. Most sign left by deer will only tell that a deer has been through. The key is to catch them in the act.