I remember those days!
I taught wilderness survival up in the ADK's for a summer... but we didn't bring any mylar blankets. I have used them in the past, when a whole load of gear got absolutely soaked in 33F water, middle of winter! It was the coldest night I've ever spent, but I must admit that I DID wake up in the morning. ;)
I think I'll experiment by using a thin quilt (the kind for sitting in the living-room!) surrounded by a layer of the Insul-Bright. In the other thread, it was mentioned that the Insul-Bright should be kept around 3/4" from body heat...
It should be pretty obvious if the Insul-Bright makes a big difference.