Nose Weight Limits

My car has a nose weight limit of 80kgs. I've seen a recommendation that nose weight should be about 7% of the caravan weight. In my caravans case this would work out at 86kgs. Do I reduce my van nose weight to 80kgs (my cars limit) or do I take it lower. Should I be towing with the max nose weight my car can take after all when accelerating and breaking the forces on the tow ball must vary and occasionally go above the set weight.