Think I am going to sacrifice an old premo down bag with 850+ down and build a few things.

One item I want to build a SUL 3 season 35dF quilt but mostly for moderate weather.
Never have read what the effective cutoff is with sewn thru baffles.

Thinking 2" but also wondering would it be much warmer with 2.5 or 3" baffles ??
Just curious.

I know its best to box baffle for cold weather eq, but I live in a warm environment and will use continuous baffles so I can shake the down out if need be.

Have a good 15dF down bag so I am good to go with cold weather.

Also is 5 mm silk down proof ?? I know no DWR but curious. I have quite a bit of it.
Thinking like a M55 outer shell with silk shell inserts I can interchange or add to.
A silk inner shell would add 3 oz per and a little warmth.

Thanks

Silk isn't calendared like downproof nylon so most likely not useable. You can always make a pillow to test out (under fill it, overfilling a pillow stabilizes the down enough to not make a decent test).

As for sewn through baffles. The general wisdom is that due to cold spots they're only good to around 35dF. Sure the thicker you make it, those thick portions will be toasty but the seams will still be frigid. It's a weird tiger striping sensation of temperature.

So unless you make the baffles so big that they kind of form baffles anyway then 2" is probably the max usefuleness and anymore would just be dead weight. Of course YMMV with how you deal with cold spots.

Thanks