Besides the BBB how do you fight claim resolution against FedEx

I shipped a subwoofer to a buyer with FedEx and despite packing it with hard foam and double boxing it, the subwoofer was damaged in transit, most likely dropped.  FedEx denied my $350 claim. Interestingly, I was the receiver of a subwoofer that was damaged in transit a few weeks ago.  It seems that FedEx is not too good at shipping fragile items. Has anyone had such experience withe this company and were you successful in your claim?  thanks.