Insulation to the ground is VERY important. When camping, I always had a 3" thick foam mattress, or earlier a 2" with a 1" on top. My feet, nowadays suffer from cold. Poor circulation or due to neck injury. The jury is still out. I thought that was part and parcel to MS, but the specialist said now, was likely due to your degenerating neck disks. I didn't even know she had that in my file.
The only time I don't wear socks to bed is during the summer months when the temp inside the house is above 66/7F (18.8C).
My "Toaster" has extra insulation in the foot area. Didn't need socks in it and was 3 or 4 degrees below freezing last time I camped with that bag (spring gopher shoot) near the end of April.