I also have a alpha 40. The prop that I found works best for me is a 10x8. It does slow the engine down but it gives a considerable bit more amount of pull in my opinion. I started with the 10x6 but found that the 10x8 gives me more room to work with. As for spinners I just bought an aluminum spinner and a washer. I have not had a single problem with the spinner since I bought it.