In my opinion, poly viscose is the best lightweight material for hiking, I do a lot around the Highlands of Tasmania and I find this material just great.

I mostly wear a USA kilt 8 yard PV, it has enough weight to keep it down in the wind, but light enough in hot weather.

I recently wore one in the Rockies up to 10,500 feet on a really hot day.

The only time I've worn heavy wool when hiking is when it's really cold (like snowing).