Seriously, you dont need more than one chaff in an FDL.. if your flying and your getting hit often, then your not flying the FDL correctly. Chaff is an emergency use only item. In an FDL you should always be above, below or behind your target. Chaff should only be used for those instances where you have been outmaneuvered, in which case you should slap your hand with a stick also, as there is no excuse for being outmaneuvered in an FDL

) lol
Seriously though, I have said this many times.. ALWAYS.. ALWAYS put pips to engines in the FDL.. forget pips to shields, unless your boosting away or topping up after combat. If you do this, you will rarely ever use chaff, and yes, even in PVP..
Give it a try, and use your thrusters to maximum effect, Boost using directional thrusters for added control.. TRUST ME.. you will see a MASSIVE improvement.