Hi there! I just wanted to follow up about the Malpais. I was able to test it out this weekend while trying to summit a 14ner in Colorado. I made it to about 13500 and had to turn back due to high winds and low temps. -20 was the windshield forecast at the summit, but I wasn't quite that high. Around 13,000 feet, I did throw the Malpais on over a thin merino base layer, Patagonia capilene mid-layer, and a Sierra Designs windshirt. So four thin active layers in total.
Anyway, it seemed to do the trick. I was not cold in the high winds when I added the Malpais. I actually had cold problems with my legs and hands, but not my torso.
So, I think for dry west windy and winter conditions, it works great as an active layer. I'll try skiing with it later this season too.