I have some questions about polyester. I'm a larger guy that tends to overheat pretty quickly and with summer here I want to stay cool. What I'm looking for are some lightweight, breathable short sleeve button downs to wear casually on the weekend. I'm having a tough time finding linen that doesn't hang like a potato sack or even finding linen-cotton blends locally in San Diego. So I decide to check out my local REI, figuring that people who hike/camp know a thing or two about staying cool. Imagine my surprise that most of what I found were poly, rayon, or some poly blend. I've always understood that for (among other reasons) polyester was to be eschewed in favor of natural fibers in terms of breathability. However, it seems that polyester and blends are used for wicking away sweat. But if polyester is so unbreathable is the trade-off for wicking worth it? Should I be looking at polyester undershirts that wick rather than cotton undershirts? Or does polyester really do breathe well and wick at the same time? Although, if my few poly button down casual shirts are any indication, they don't breath well at all! Inquiring minds want to know! Oh, and as a side note, I did see a shirt at REI.com that was made of soy fabric! How breathable is that?