i went out over the weekend and camped one night in the bivy in a shelter and the second night under the stars in the bivy. the second night i had no wind protection, just the bivy.
these items were all inside the REI minimalist bivy:
Ridgerest foam pad
REI 1.5 core mattress
Marmot Sawtooth 600 fill down sleeping bag
i was plenty warm in the bag unless my knee, foot, hip, or shoulder compressed the sleeping bag above me when i moved around while sleeping. i would get a very cold spot in the area that was compressing the bag and it was very uncomfortable. i did not get much sleep because i forced myself to lay on my back and not move so i could stay warm.
anyone have any suggestions on minimizing this issue?