The current 1040 system design (one in world download), the system can smelt 374,400 items per hour.

Features:
- Dolphins allow item recycling (5 minute item despawn timer to be reset) at 4.7 million items per hour
- System is modular. In each row of furnaces there is 80 furnaces with 40 per side. You can have at little as 1 row of furnaces or 1,000+ rows of furnaces (in theory, provided you have other players to render all hopper minecarts and entities in the distance)
- On / Off switch to reduce lag when not using system and prevent hopper minecarts from having issues when loading and unloading chunks they are in
- Not ridiculously complicated unlike other huge furnace arrays