I'm nearing the end of all of the necessary gear purchases for my AT/IAT thruhike next year, but still have a few tiny items like underwear to purchase. I'm decided on smartwool while hiking to hide the funk, and then the newer version of capilene for around camp. I know that the capline will be either Capilene 3 or 4, to make sure that I can stay warm while sitting still. I'm unsure about the tickness to wear while hiking. I know that some people just hike in shorts and shortsleeves, so the answers may vary wildly. I tend to get pretty cold while sitting still, but not sure about while moving since I"ve never hiked in thermal layers before other than heavy and hot thermal cotton tops and bottoms. My worry about Microweight is that it would be great while moving, but when you stand still, you'd get too cold while eating, etc. The lightweight would probably be great for standing still to help fight off the chill, but while moving may cause you to generate too much heat after hiking for 30 minutes.