A little fuzzy on that one. By the time it gets to the end of the pond, it's total flood and there isn't a bright spot any more. It's not a thrower, but I wasn't trying for that anyhow.
That Copper shot idea is brilliant, more heat capacity less weight. Looks like a good mod step for thin Aluminum heat sinks on those multiple LED supper lights.
No good reason other than that’s what I have always used. It started with soldering water pipes way back when and I just stuck with it, rosin core 60/40.