How does bee armor sleek bonus stack?

[Deceptive Pastry]

Wiki for slow shot says "Ranged attacks have a 50% chance to slow targets by 20% for 5 seconds when hit." That is only for one piece though right? So what happens when you have 3 pieces of it sleek? Or does the bonus not stack.

Also marksman cap gives +Crit Energize: Bow. But base crit chance is 0, so this hat does nothing (non-sleek) if you aren't using Coup De Grass yes?

[Kisama]

Maining a bow I feel like you'd virtually always want Coup anyway, even the 2.5% one.