400grams of insulation should be plenty at 20degree. I use only 200 down to zero.
Man I would look into your sock system and insoles first. I bet you have sweaty feet. Perspiration can significantly downgrade the value of the insulation.
I would suggest trying a thermal liner sock, with a vapor barrier sock over(prevents insulation from getting wet), then a thick bison down sock(warmer than wool) over that. Yes 3 socks. Hopefully you have a boot size bigger than your normal for winter use with thick socks. I use a full size up.
Seriously warm-Surprisingly soft, we created a sock from Bison down and superfine merino wool that will keep your feet warm and dry all winter long.
thebuffalowoolco.com
Not sure if kenetreks has insulated sole but could add a aerogel insole as well.
Amazon.com: Safety Works CTFM Toasty Feet Mens Shoe insoles Infused with Aerogel for Sizes 8-12: Home Improvement
www.amazon.com
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