Here is the trick. Bossk Fires normal and choose someone that you have the LEAST chance of hitting. You have rage going so you re-roll TO MISS. Now that you've missed, you get 2 attacks with Bossk (See Gunner FAQ) First with the IG88B ability using your Mangler Cannon (Rage still takes effect) use Bossk to boost that one, then again with Gunner Ability (still rage). You can use the focus token on either of the attacks you WANT to hit with. Don't forget to Boost damage with Bossk's ability on both striking attacks, should be easy with the Mangler and highly probably on the standard attack. None of these attacks have to be on the missed target so you can theoretically finish 2 ships in 1 turn (firing at three) with just Bossk. I'd Keep IG-88B Behind the YV-666, and Capitalize on the distance to use the HLC's.

Another possibility is to adjust the IGGY to use the Mangler with autothrusters for the late game/wiping out stupid turret cling-ons and slicer tools to affect the aces trying to come up from behind.

adjustments? do you prefer HLC or Mangler on Aggressor

Here's my current triple-shot Bossk list.

[IGGBOSSK]

IG88-B (45)
Aggressor (36), Fearlessness (1), Fire-Control System (2), “Mangler” Cannon (4), IG-2000 (0), Autothrusters (2)

Bossk (55)
YV-666 (35), Saturation Salvo (1), “Mangler” Cannon (4), Cruise Missiles (3), IG-88D (1), Dengar (3), Gunner (5), Glitterstim (2), Munitions Failsafe (1)

This way you potentially hurt the bads with every stage of the triple-tap, as the initial miss with a Cruise Missile hurts everyone at range one of target with less than 3 Agility(Thanks, Saturation Salvo!), then just hit the next 2 shots, with Dengar rerolls and Glitterstim superfocus. Tasty, rude, and unneccessarily overwhelming firepower. Secret bonus: Your IGbro won't be splashed by your salvo, that chrome goliath is too swift! If loving Scum is wrong, I dont wanna be right.

How does the double tap with Gunner work? Gunner says you immediately perform and attack and can not attack again this round. It seems like you wouldn't be able to trigger IG88-B's ability after Gunner and if you chose to use IG's ability and hit you wouldn't trigger Gunner. Am I missing something?

If you look at the FAQ, you get to choose the order. You use IG88's ability to fire again, and then you use Gunners. Both are "immediately" even though only 1 has it in words. Make sure you fire the Cannon second, otherwise you screw it up, but as long as you follow the correct pattern it's legit. FAQ's link is right here. https://images-cdn.fantasyflightgames.com/filer_public/56/62/566241f9-7d71-4871-a721-fc4ce371ba67/x-wing_faq_v440.pdf