It should probably take twice the time too, no? If we combine the two lava recipes. The next part is IMHO

I like the general idea, but if we are going from the assumption that normal recipes output the unwanted metal as part of the stone byproduct, the ratio of copper to iron should be be more like 200:300 and not 250:250. And we keep the stone quantity the same for balance reasons.

Yeah, both the crafting time and results were just an initial guess.

I was afraid double the crafting time could be annoying in terms of throughput, so I went for the time of one of the normal recipes. Playing a little with the mod, and taking a look at other factories of mine, I notice copper is used much more than iron, so an equal ratio already is decent in terms of making you balance things.

As I said though, these were guesses, and I'm open to changing it in the near future with more playtesting and/or feedback.