I’ve just begun playing a few days ago, loving the game very much. However, I noticed certain bottlenecks in my production line, but not at the slower slots. Certain slots that require very little time but multiple types of material seem to be the problem. Take fit brakes for example, of the 16 slots it can stockpile, it brings in 15 brakes and only 1 servo, while per car the ratio is 4:1. This is slowing down the entire line because that one servo has to be brought in, and having another stockpile nearby just for servos doesn’t seem to fix the problem. It would be very nice to set slot stockpiles just like generic stockpiles to determine exactly how many of each part to come in.
Nope - It seems they are set. So I find that fit brakes - fit lights - fit seats - and fit lighting always have a bottleneck there. Best you can do is put a mini supply stockpile right next to it with all servos - or add more fit brake slots to improve the throughput.