RE: aluminum spinner for 2 stroke
A 2 1/2" one will be fine. I don't know of any 2 1/2" spinner on the market that would not work on an OS .46.
The size won't make any difference and an aluminum one will be better than a plastic one that may come apart at high rpm. The only plastic spinners I like are the Great Planes ones with an aluminum backplate. The plastic backplates tend to distort and are, in my opinion, dangerous on a 4-stroke.