For my 2016 thruhike, I'm planning on using the Under Armor Heat Gear short sleeve undershirt (which I'll wear all the time) with the Smartwool 250 midweight when needed. I still have on my gear list an REI fleece AND a Marmot Zeus down jacket. I know I don't need the fleece and the Zeus, but I can't decide which one to leave behind. I've rationalized the Zeus will be warmer, but the fleece better in wet conditions. Sorry for taking this off the topic of base layers. Suggestions?