You got the right idea with the Ac20 and Dual Lasers, just make them standard Large instead of Er. That should give you much more firing time instead of having to worry about shutting down. Here's the config I use for that:
CTF-1XIt still has a lot of armour, even though the arms only serve as temporary shields. Protect your right torso and save those ac20 shots for when they count, otherwise keep firing those large lasers every chance you get and you should be doing better than 300dmg most games.