biweaves are absolutely the wrong kind of shields to fit on a trader that you don't intend to keep around in the area to fight lots of opponents one after the other. They might have a great recharge rate, but they only have the total strength of class D shields of the same size.
And, of course, it depends on what size shield you've decided to fit.
I mean, a C8/C7 shield is taking up a lot of cargo space on a cargo ship so maybe it'll be okay to just fit C6 or C5 shields instead, right?