Method of attachment is thermal glue. The mass of the heat sink, well given its going into a C cell Mag lite im sure you could imagine how big it is. There is no air its submerged in water (except for the small amount of air in the Mag). The mass of water? Pacific ocean or small lake. I doubt it would make any diffrence.
I dont really need a totally scientific calculation done. Just want to know if anyone has had any problems with running this many LEDs in a mag at high current.