Where there is a will there is a way.
Why do you want to add a fin?
It won't be easy, and if you mess it up you could sink your boat (imagin a fin sized hole in the bottom). You can't just drill two bolt holes through the bottom and bolt the fin up, it needs to seat against a well reinforced portion of the bottom. I would expect that you would need to cut out a fairly oversized section and glass in a sturdy solid piece.
I haven't paid attention to my current boat, but the previous two boats, which were direct drives, the mounts for the tracking fins were tied into the engine mount and ski pole mount. Big metal plates fastened down to the hull.
I just can't imagin what benefit you would get for all that work.