Yep think you probably going to need more insulation
U will be cold unless it's unseasonably warm. If u get a high R rated pad (above 5) and wear down or primaloft jackets and pants u may get away with it.
I concur....wear a bunch of clothes and puffys unless there is a heat wave. But otherwise you'll be cold...also the wind at 12k can crush you at night...I suggest a tent and a 20 degree or less bag or quilt. But me...I like good sleep. So I carry more weight with my bag\tent\pad\pillow set up and cut where I can else where...the better I sleep...the harder I hunt...I've learned the hard way...