The body's ability to uptake glucose at An Accelerated rate is Moreso the first 24 hours of a load than the second. As such, I would count on doing a majority of the work the day before your show and then playing it by eAr (judging how you look) the day of. I've heard figures that a depleted average adult male can store about 500-600 grams, but I'm always skeptical and prefer not to have an exact number in mind.
Still, banking on a good 400-500g load for someone weighing about 150-175 lbs and then focusing on "topping off" or even playing it safe Contest day is usually a pretty good ballpark.
I'm not a fan of those few individuals on social media bragging about loading in 1000g the day before just trying to get people riled. Nothing worse than ruining a 20 week prep on the last day by trying to be a badass.