So I tried to set it up to keep exactly 10 items in a chest, but excess items don't get removed.

Adding an extraction module just makes the whole thing insert and instantly remove the items again.

I think a checkbox to remove excess items or a check on the extraction module to NOT extract items in the Stock module would be good.

Oh also, if there are not enough items in the system to satisfy the number of items, an option to NOT stock them in that case would be nice

Currently neither of these are part of the design, but I like the idea of toggles for them so will probably add it. :)