I don't get the wear one carry one on the zip off pants. Why bring two of anything, especially an outer layer. Underwear and socks maybe, but even those I only bring in different sizes and thicknesses. If clothing gets wet, wear it until it is dry. I bring the same clothing for 20 days as 2 days. Totally agree with wearing wool, but washing underwear on the trail isn't that tough either. Soak in boiling water, squeeze dry, wear on head until dry.