Using a Platy for this would kind of scare me.
I've had 2 of those develop leaks for no apparent reason. I think it's very important to point out that it's risky enough taking water (even hot) to bed with you when temps are hostile. What are you going to do if you, your clothing, your quilts, and your hammock get wet when temps are below freezing? You probably won't notice until the water has had a chance to soak several items and cool down. That's a lot of push-ups and jumping jacks to do to get and stay warm.
I always start thinking worst case scenarios when I'm doing something like this and I try to minimize those risks as much as possible. In this instance, I choose the most reliable container I can; that ain't no Platy.