25x (quick smelt) smelting sounds & worked fine imo (maybe reduced to 20x or 15x) Just wood consumption shouldn't be crazy (campfires
@"Lil Daddy Micah" ) so how it was at 2.5x the original speed would be better
6 wood per minute x 2.5 = 15 Coal (Campfires)
30 wood per minute x 2.5 = 75 Coal (Furnace) x 6 furnaces = 450 Coal
Instead of:
6 wood per minute x 25 = 150 Coal(Campfires)
30 wood per minute x 25 = 750 Coal(Furnace) x 6 furnaces = 4500 Coal
considering the fact you can easily have 6 furnaces at any one house your charcoal can quickly add up, so it's not necessary at all to have it at a high multiplier