The phrase "hunched down" can be replaced with various synonyms, each with slightly different connotations. "Crouched down" suggests a lower and more stable position, while "bent over" may imply more of a forward lean. "Hunkered down" conveys a sense of settling in for a longer period of time, while "squatting" implies more of an active stance. "Huddled down" could suggest being in a group or seeking comfort, while "curled up" implies a protective position. Finally, "stooped" implies a slightly older or more feeble posture. Each of these synonyms can help create a specific mood or tone in writing depending on the context.