A jacket that feels comfortable in town can feel bulky once you add a rucksack. Before a long walk, try your layers with your pack on — not just in front of the mirror.
Put on the clothes you plan to wear, shoulder your loaded pack and walk around for a few minutes. Reach forwards, lift your arms and turn your shoulders. Notice any fabric bunching beneath the straps or a hem riding up as you move.
If something catches or rubs, adjust the layers before you leave. Sometimes a smoother arrangement or one less bulky piece makes all the difference.
Do the same check when changing layers mid-walk. What fits neatly without a pack may sit differently underneath one.
Field tip: Test your layers under your rucksack, not just on the hanger.