Mostly because reading lately I have seen climashield estimates all over the place.
Until a couple of days ago I was using the numbers 2.5=45dF, 3.7=35dF, 5oz=25dF but now after reading that seems to be overly optimistic and I dont like to wake up freezing.
So now what I am building is this.
M90 shell with one layer of 3.3oz apex with a drawstring footbox.
I will be able to open the shell and add another layer of insulation inside.
I might add a layer of 5mm silk on the inside on top of the 3.3oz CS but I have not decided yet.
Right now the second layer of insulation will be 5 oz Climashield Apex in a 5mm silk (0.5oz) shell.
I figure the base quilt should be good to 40-45dF or so and with the additional layer maybe 20-25dF with a base layer and socks.
So the total for cold weather will be outside M90, inside one layer of 3.3oz plus one layer of 5oz, 2-3 layers of silk.
Size is exactly 3 yards so the base quilt without the 5mm silk will weigh 17.5-18 oz.
The additional 5mm silk covered/5oz apex will weigh 18oz.
The 5mm silk weighs 1.5 oz per layer.
I already have a very small 2.5CS M90 quilt just for summer that weighs 12.8oz.