Never mind, I figured it out. Yetis are in the Himalayas and Seal live in the Arctic Circle. They don't have any problems with each other.
Last night I tried staying out. From about 10pm-2am, I slept like a baby, but then something happened, and I lost my good seal, and away went total comfort for the night.
I'm not sure what happened. The shock cord may have stretched; I might have slid towards the foot end without realizing it.
My first solution was to slide the yeti back down to where I was (align with neck). That worked for a little while. Then, I tried to use my headlamp to make a triangle thingee. I took both sides of the shock cord and used the headlamp to girth hitch them around the ridgeline. I think that may have been my big mistake.
Even though I had a really good seal at both ends now, there was a huge gap between the bottom of the hammock and the UQ.
Either way, I suffered for an hour, then bailed. CBS just wasn't worth it to me.
What do you think I could have done differently, so that I maintained a good seal and full hammock/UQ contact all night?