>>713186602
No filtered wagons, you get one train and dump it, and it the item count of that item is less than (number of wagons(item stack size*slots in wagon))/2, trigger a signal so the train fetches another load of that item. Sure, I use warehouses in this design, mostly because fuck balancing, but I'm 99% sure you could do this with regular steel chests by filtering the unloader inserters