Im 5ft 8 and weigh 78kg of muscle, should i fight at light-heavweight or lose weight and fight at middleweight?

i do kickboxing and i have a tournament in 2months at my weight at the moment means i fight at light-heavyweight but im worried that these guys maybe too tall for me. the other alternative is to fight at middleweight but i'll have to lose 6pounds which im not sure i can do as i already follow a really clean diet, and if i dehydrate my self i feel i my be very weak as i weigh in only one hour before i fight.