I've seen what other people do for their trains, and what seems to work for me is for a large stop such as a smelter, or main bus unloader

Has one entrance with a chain signal.
The track then splits into a stacker that is however wide as your needs. The start of the stacker has a regular signal on ...

So I just finished running a bunch of numbers for the new science packs, and realized that the old main bus ratios are now way off, iron has been greatly reduced in demand.

These numbers were all ran using assembler 2's (0.75 speed) and assuming you would like 2 setups so 10 red science pack ...