For those still having trouble sinking ships you should definitly be able to sink a cargo ship with this bird, will take about 19 shots, just aim centre hull and always try and hit the same place, make sure your attackng angle is around 45 degrees nose down, and you should be fine, obviously 19 shots is alot, so if you have your wingmen attacking the same boat, just reley in.
Also make sure you are using AP ammo.