Since the aluminum has a better thermal conductance than copper, that's my theory. Problem is once you put it in there with the thermal tape...it's in there and there is no getting it back out without destroying the led. As a product designer...it looks like the inevitable trade of was between aesthetic accuracy and functionality in terms of future maintenance if the led ever needs replaced. Best bet would be to ask the designer of the emitter how he would suggest holding the led and lens place. To me that is more of an issue than how do I add the copper heatsink, when the entire emitter is already setup to be the heatsink.