I'm putting together a scum list and want to get the most mileage out of Bossk's ability. in your opinion is it better to run him with a mangler cannon or with a mercenary co-pilot? the YV-666 in my list will have one of the two and engine upgrade only.

Merc Co-pilot is not an option. Too restrictive without improving your chances of actually hitting.

If you want slim, Calculation is the way to go. 1 pt and he actually has the EPT slot to equip it. Although wasting 3 crew slots from such a fine selection is a waste.

That's perfect. I can add Calculation and keep Merc co pilot as well.

I usually run Bossk with "Mangler," but I've found that I take a lot of primary attacks at range 1 and still get quite a few critical hit results. For me, K4 Security Droid is a better way to run a slim Bossk. But I haven't tried Calculation yet, so it may be worth it.

Merc Copilot is mostly a waste on this ship. You MAYBE get to use it once, but never again for the whole game. And you're using it when you're already at a disadvantage.

Instead, consider grabbing Calculation, Greedo, and Boba Crew. IMO, this combos nicely with Bossk's ability and creates a solid Fett-Ex delivery plan.