"is why I recommend layering scheme using a mid layer like Power Stretch or R1 with a windshirt and higher loft insulation with 100g or greater synthetc fill, or down in drier climates."
But, just doing the arithmetic, fleece or fabric have much lower warmth per weight.
Better to have base layer, insulation layer, jacket - and that's it.
When hiking, just base layer and jacket - that works for me down to 20 F but just barely, I have to hike briskly to stay warm. If that isn't enough to stay warm in a particular condition, then I concede mid layer is good.
Having a warm hat and/or hood can sometimes keep you warm with just base layer and jacket, and you can easily remove when you get too warm.
To put it another way, rather than carrying a mid layer that weighs 10 ounces, have an insulation layer that weighs 2 ounces more than you would have otherwise.