DoubleFurnace/QuadFurnace

• 2x smelting speed (2.5x when upgraded)
• 4 input slots, 2 fuel slots, 8 output slots
• Crafted from 2x Furnace at a Workbench
• Upgrade cost: 10x each of Copper, Iron, Thorium, Cobalt bars

• 4x smelting speed (~6.7x when upgraded)
• 8 input slots, 3 fuel slots, 8 output slots
• Crafted from 2x Double Furnace at a Workbench
• Upgrade cost: 20x each of Copper, Iron, Thorium, Cobalt bars

make sure to make new furnaces when the mod is installed as they require metadata to then craft the double and quad furnace