Not sure how many will read this but... This set up requires the user to manually hit the buttons to add or subtract engines from the grid. So far I can't think of a way to automate this based on SU usage. But I think if you designate and engine to a specific factory and link it in tandem with the content observers used to shut down the factory when full you might be able to shutdown the engine or start it up using the same signal??? Let me know or post a modification if it can work.