I went with steel because I don't have the means to weld aluminum. Found a piece of steel tubing and welded a steel plate on the back, grinded it smooth and painted it with black acrylic paint that dried matte.
I had a 2.2W 445nm laser around 40cm away shooting into it for a full minute and it didn't even get warm. Works good I'd say, I'll try it with Arcane 635nm when I get it for it's full 4 minute duty cycle and see if it gets warm.
