I find speaking up to be very effective. I was on the 112 overnight and followed my recent custom of asking upon boarding that the temperature be kept at 20 or less. It got somewhat warm about halfway through, but a quick comment had the cabin nice and cool in minutes. I always ask in advance now, so that the first thought on their minds is people getting too hot, not people getting too cold. After all, those sensitive to cold can easily add layers or use a blanket. Those of us who run hot can't very well sit in our skivvies all night!