I would recommend you take it to someone who has repaired airboat hulls before. The front tabs of your rigging experience a lot of stress. They will want to determine why the stringer failed such as was it from stress, impact or wood rot.
A lighter boat has more flex than a stiff heavy boat. They tend to run dry real well but cracks at stiffeners and stringers can be troublesome if the boat gets used rough.
Wood rot is another real common problem and can happen quick if bolts holding the rigging on are not given a little 5200 type sealer to keep moisture out. If someone has drilled holes and moved rigging around and not resealed the holes that will get rot really fast.
Hope this helps explain things.