RZ-2 A-wing with composure.

Action = Evade, then ability triggers to perform a Red boost that fails. Does Composure work in time or does the stress block the whole thing?

you get stressed as you fail the action, so no focus action for you.

Also composure requires you to have no green tokens so you can't use it when you have an evade token anyway.

Well I meant just the theory. Could have been a roll or a lock or whatever.

Still this is basically what I thought I just wanted confirmation.

Composure is still decent in context, by the by. You just use it to insure your risky FIRST reposition, which might fail, then get your focus and do the second reposition using the ship ability.

Actually, Composure says:

After you fail an action, if you have no green tokens, you may perform a action.

While the relevant entry in the rulebook is:
After a red action fails, the ship gains a stress token .

In other words, it seems like the timing window for both effects is the same, which would allow the player in question to resolve them in order of his choice. It's definitely something that needs to be clarified in the FAQ but for now as per RAW I see no reason why that combo shouldn't work.

EDIT: Nevermind, I guess I got carried away. Stress token is a game effect, not an ability, so it goes in first. Too bad. Would have been nice on L'ulo.