This is how I have mine kitted out:
http://www.edshipyard.com/#/L=70O,4zh4yH4yH7OX7OX0Wg01Q0_g,2-7_7_6Q6u9Y6Q5A,7Sk0720724xo0nE
The excess power issue sorted by disabling the cargo hatch.
I tried it with the the class 4 cannon in the huge hardpoint but it just didn't work for me. Much happier with C3 gimballed beam. I love the ship so don't mind the hit in weapons power.
Upgrading the bulkhead to a Military Grade Composite costs a whopping Cr46M! Personally I don't think it's worth it or needed. If the shields are down and the hulls taking damage its time to leave! You shouldn't have to run away from and NPC engagements (I haven't had to, yet...) but at least in that scenario the FDL's speed will see you to safety.
I only play in solo so can't comment on its PVP capability but with this loadout I can handle NPC Elite Anaconda's.
I love the FDL so I admit to being biased!