It is sensible to be prepared to ballast, Do not rely on the caravan manufacturers statement of ex works nose load, That is state of affairs that you will never encounter even when dragging the brand new caravan off the dealers forecourt. Because as soon as you add any sort of load to the caravan the nose load will change.
I once had to collect a second hand Twin Axle unit and the experience was unpleasant because the nose load was too small. and within the normal range of towing movement whilst going over speed humps, the actual nose load switched from Positive to negative, which gave the tow vehicle a double tug at the hitch. I had to ballast up the the front of the trailer to ensure the nose load always remained positive.