Yah, here ya go…
On an Al star, it’s already peaked at about 1.8A and light output will decrease with more current.
On a Cu star, the difference on the graph is 460lm at 2.0A, and 480lm at 2.4A. 400mA more current (20), only 20lm more light (4).
GUARANTEED you wouldn’t be able to tell the difference visually, even side-by-side.