i'm new to metallurgy, but i think i found a bug here that is pretty significant. (actually not sure if its the metallurgy furnaces or if its the nether ores mod, because i didn't test this with the vanilla furnace, just the iron furnace).
when i place nether ores (redstone, coal) inside an iron furnace (metallurgy), the FIRST nether ore gives me 2 overworld ores. but if i leave the furnace cooking and let the cooked slot fill up... the subsequent ores still cooking only give me 1 ore per, and it stops cooking when the cooked slot reaches 15.
so, if i cook 16 nether ores, i should get 32 normal ores, but i dont... unless i manually monitor the furnace and pull out the ores EVERY time one gets cooked. every time 1 turns to 2 i have to clear out the cooked slot of the furnace to ensure that the next one also give me 2. otherwise it will give me 2 for the first, the 1 for all after.
unmonitored: 2, 1, 1, 1, 1, 1, 1, 1, up to 15 furnace stops due to stack size, clear out cooked slot to cook remaining, get 2 for the initial again, then 1 for the rest.... so its 16 nether ores = 18? normal ores
monitored: 2 (remove) 2 (remove) repeat = 16 nether ores = 32 ores!