so do you know what the gi weighs? will you be at the tournament location the day before you fight? will you have access to a calibrated scale the day before? how long do you actually have between weigh-in and fight?
water will be your biggest concern--16 oz = 1 lb. controlling weight in that short time frame can be done pretty well just by manipulating water consumption.
if you want to get giggy, find an accurate scale to get a baseline on yourself. then bring a food scale. figure out what your margin is and eat weighed food & water accordingly. if you have at least an hour or two between weigh-ins and fight, you'll be able to rehydrate pretty well. just pound a bunch of water immediately after weighing in--the faster you drink it, the faster it will empty from the stomach. this should also give you time to •••• out any the kidneys reject.