I'd skip the guesswork on temperature and get a cheap instant-read thermometer early. Also, I'd bring a small insulated sleeve for the brewer—something like a neoprene cozy—instead of improvising with a towel. It's steadier and less fiddly.

And one more thing: if you're brewing outside (camping, tailgating), consider a wider thermos for preheating water and a wind barrier around your setup. Wind is the silent killer of pour-over heat.