Deep cold down gear Deep baffles or double layer??

Good question, I wonder that also

If you have big baffles, then the down will easily shift to one side.  Hard to keep all the baffles evenly full.  If you had two layers with baffles half as thick, there would be less shifting.  But then there’s an extra layer of fabric, but with ultralight fabrics that’s not that big a deal.

hmmm….

With the Egge duvet the space between the UL mesh used to keep the down in place was also lightly filled with down. Interestingly the same technique is also used for the foot section of my UL winter sleeping bag and it works very well.

Naturally I’d use a larger shell size for the outer, you still need the differential cut

No-See-Em mesh is a half ounce/ 13GSM; that wouldn’t be much more weight than 25mm baffles and perhaps a lot less work.

Egge used a space-filler cut for the inner layers in their Expedition down wear to allow maximum lofting of the fill

I have another thought about clothing for deep cold also. There have been many instances of Antarctic expeditioners being evacuated because of frostbite while skiing and sled hauling recently. Mostly with severely frostbitten thighs.

It.s because modern LW and UL expedition gear used a high fill-power down that collapses under wind pressure. Several makers now use a layer of synthetic insulation in specific areas to counter this collapse, some use Thinsulate, some use Primaloft but some use Polargard Alpha

If I was to use a light layer of Thinsulate I would use it on the inner side but if I was to use Alpha would it be best there or as a layer in between the two down layers?

Mill Yardage currently has 60GSM Alpha which I think is as heavy as I would like to go