Watch the next meteor shower from a beach in Hawaii?

I was going to suggest the head cover and hot water bottle at your feet, but those already mentioned.

Maybe the fleece blanket inside the sleeping bag instead of on top.

I can also envision a Blast burito, with Blast rolled up in a wool blanket, inside a bivy bag, on top of a foam pad, on ground high enough for fog not to roll down onto you, with a wool cap and foot warmer. Just got your face showing out of the bivy puka watching the stars.