I have been using about 2000 to 2500 for the full and about 3000 to 3500 for the half. But in all honesty it is a guess at this point in time. For instance, the elite corral is not considered in my method nor are the couple hundred unused bib numbers at the bottom end of the numbers. Also, the back corals tend to be a little larger than the front and middle ones.
The official placing will not be known until the expo and you get your bib.....