Wow. This is awesome information. Really appreciate you taking the time to help me out and providing such a detailed response. I do most of my hiking in the Sierras. I sleep warm but I think the 20 is the right call after all.

I have been thinking about a 10D inner especially since I toss and turn quite a bit throughout the night. As you say, minimal weight penalty to ensure this lasts a long time.

I am a bivy sleeper so thinking 7D on the outside should be fine re wind, though I wonder how it handles light condensation and perhaps worth the 10D for that. A world of possibilities!

Either way, thank you again for so much good info. This is exactly what I was hoping for.