Most Banana Boats came from the factory with 280 K-planes. The only exception was the single engine boats such as yours and mine that had none as they weren't really needed because of the slower speeds.
I always said that with my 200hp merc hanging on the transom all I needed was a tab on the left side. Reason being is with the prop spinning clockwise, the bow would hit a bit harder when taking a wave to port.
If your running single engine, then I can say for sure that any type of tab will work.
The exception is if your running set back or a surface running prop.
Last year I ran 18" of hydraulic setback and a 20" shaft with approx 350hp running on the surface. Lots and Lots of torque and I had not installed any tabs yet.....
As for the longer tabs? If your running on the transom, then the 380 tabs are a waist of money, unless you are going to run them flat (meaning parrallel to the water, not the shape of the hull), then it is a great idea.
If your using any set back greater than 5-6 inches, then 280s are more than enough.
If your going to hang on the transom single engine, then save a bunch of money and throw some bennetts on the back.
Hope I helped...