Be careful with the chaff launcher; it's only effective against gimballed and turreted weapons, and the pirates might well be using fixed. Since the update, NPCs are much more aggressive and it would serve you well to just run if you are interdicted.
In short, don't get cocky.
Given the limitation of the Hauler, I'd personally suggest an Adder - it has similar cargo capacity, but gives you a single medium hardpoint and two small hardpoints. If you can afford to equip them, you're got much greater potential to look after yourself in combat from the (now inevitable) interdictions by the (now) psychopathic ships that just start firing the moment you're in range.
An Adder can give you 22t with a class 2 shield generator (beware: they're very weak, but they will soak up a few hits before they fold, giving you some extra running away time).
Here's a basic loadout.
With the proper shield generator (class 3), your survivability is much better (and upgrades to the shields cost more), although it limits you to 18t of cargo.
Here.
Whatever you decide, I'd suggest that the priority upgrade should be your power distributor. With an upgrade there, you will be able to charge your boosts faster. Basically, it will help you to run away.