hes making an obscene cut first off, being his height and a couple pounds heavier at a little lower body fat i have contemplated such leaps but they have never seemed reasonable in terms of strength and stamina degradation.
dont do the velocity diet you dont want to cut out all your carbs leading up to a fight and kill your gas tank and recovery capacity.
fix his fucking diet!! i dont know what you have to be eating to sit at 25% fat while training at a high level 5 times a week, cut the shitty food and the beer.
you shouldnt be in a situation where your needing to drop 34 pounds in order to be competitive
from what i have read in weight cutting guides and experienced myself cutting up to 10% of your weight in water is attainable and as far as you would probably want to go some people do more many do less.
if he can get to the high 180s he can make probably drop the water pound pedialite and be ok
the best answer i think though is he needs to seriously re-evaluate his training