I am in the process of mounting all my sirens in that way. Most are very top heavy and without a mounting base can easily be knocked over. Here is one of them, Federal 77GB.

In regards to curved/angled blades, at least with some vehicular sirens, Q series curved C5A angled/curved B & M angled/curved 77 doubletone straight 28 straight Sterling M30 straight http://img.photobucket.com/albums/v691/Henry455/Siren%20Rotors/Rotors.jpg Clockwise from top left, Model 28, 77,...