WARNING: DO NOT PUNCTURE ALUMINUM PLATE; FOR INTERNAL AIR FLOW. I was hoping the black plastic was spot glued. So I scored...

Acetone & Utility Knife. It dissolved the glue along the edge of the aluminum patch. Slipped the blade in between and sliced through the rest of the glue. Made sure to score deeply around the area I wanted to remove, so the plastic would snap off at the edges. Fortunately, the aluminum base plate was strong enough that it didn't puncture, but as you can see it dented quite easily. Will clean up the edges & left over glue later. For now, here's the temperature differences. (basic load = all transformers trailers @ 1080p 2x speed; just like last time) Additional temperature drop of 10°c, for a total temperature drop of 15°c, at the centre spot, which was the hottest spot before I removed any plastic from the lid. For now, I'm placing the copper heat sink & fan on top of the bare aluminum to cool it by an additional 5°c; until my 200mm case fan & 12v ac speed controller arrives. Then I'll stand the Mac Mini up vertically, apple logo facing forward with the big silent fan blowing directly on the whole bake...

Air intake is at the front of the Black Lid. If you turn your Mac Mini upside down and press along the edge of the circular lid you'll fee it is firm all the way around except where the locked / unlocked dots are. That gap is where the air enters the unibody. It flows up through the WiFi antena's swiss cheese holes over the logic board and then down to the blower fan's air intake; cooling the board components before it cools the heatsink on it's way out.