EJ - 1) The Power Stretch composition and thickness both matter for your unique chosen application:
The smooth, tightly constructed 160 denier Cordura nylon face provides superior abrasion and wind resistance. A semi-velour polyester back provides for good wicking, 3-season warmth, and next to skin comfort. Fabric has wicking/siphoning properties for moving moisture away from the body and a odor reducing treatment to inhibit the growth of odor-causing bacteria. Features four-way Lycra“ stretch for unrestricted movement. Ideal for climbing, mountain biking, and equestrian pursuits, where superior abrasion resistance, maximum freedom of movement, and clean profiles are desired.
1.38 clo/oz yd2 (my estimate from averaging other Power Stretch version manikin tests)
Stretch W/H 80/80
Double faced polyester velour with 4- way Lycra® stretch. The warmest Power Stretch® fabric. Lycra® blends give 4-way stretch for unrestricted movement. Fabric has moisture management properties and an odor reducing treatment for next to skin comfort. Ideal as a heavy, expedition weight underwear or for general cold weather layering.
1.34 clo/oz yd2 (manikin test)
Stretch W/H 100/100
A durable nylon/Lycra® face, with a non-pill, low pile polyester velour back. BiPolar construction allows the placement of different fibers front and back to handle varied conditions. The durable, smooth nylon face resists wind and abrasion, and allows for easy layering. The inner pile (back) has wicking/siphoning properties for quick drying and moving moisture away from the body, along with odor reducing protection from odor-causing bacteria. Lycra® blends give 4-way stretch for unrestricted movement. Ideal for cold weather first layer or next to skin applications such as winter running/cycling,/cross-country skiing tights, and accessories.
1.42 clo/oz yd2 (manikin test)
Stretch W/H 60/60
This #7767 material is close to what is used in my Ragged Mountain Hoody. I prefer it because it has the lowest weight and the most warmth for the weight by not dealing with heavy abrasion protection. I use a wind shirt or hard shell to protect it against hard abrasion when required.
2) I own and use a Smartwool Merino hoody, an Ibex Shak Smartwool hoody, a Power Dry Patagonia R1 hoody, and a Power Stretch Ragged Mountain hoody. Reference my 9/5/07 17:15:50 chart post for this response. For backpacking MET levels from about 45F to 0F, I find the R1 Power Dry hoody / windshirt combination provides optimal variable thermal balance with the least amount of weight. This combination also provides the highest safety margin if they get wet and need to be expediently dried by hand wringing. A Power Stretch hoody would provide a comparable comfortable temperature range but in order to not sweat, its comfort range would start at a lower temperature or lower MET level.