Wow!  I wouldn't not have thought that was possible!  I bet it will seem to be a lot louder mounted there.  I see what you mean about the pictures, it is a bit hard to tell what is going on.  Please address the following:

1) Do you think it will be blocking a significant amount of airflow to the radiator?
2) Do you think the Nautilus would be OK there with the possible amount of weather that will be thrown at it?
3) Are you concerned that the huge weight of the Nautilus compared the the stock, tiny magnetic horn, will be too much for the stock bracket and perhaps fail?

Thanks

1) I thought about that, but I don't think it's an issue. There is plenty of surface area for air flow.
2) I would think that Stebel made this unit be weather resistant...maybe not weatherproof, though. I'm not worried about it.
3) No, not at all. The stock bracket is very strong, heavy gauge steel. On top of that, others have mounted this horn with the stock bracket with using only one bolt, I'm using both bolts, which is how the bracket was intended to be used.