My Graupner Extra 300s stock spinner is about needing replacement and its size is 2 3/4". I don't want to spend 30.00 on one so I'm considering using a different size. I like those with the aluminum backplate, but GP only makes them in 2 1/2" and 3".

What size do I put on there? or,,,,,,,,,,,,,should just spend the $30 on a full aluminum.

got this aluminum spinner from these guys http://www.racingdevil.com/product.php?category_id=105 there pretty nice polished and come with the adaptor nut included with the spinner,
the one on my P-40 is a 3.5" but they have a 2.75" version as well

And I started using spinners with the brand name of MAGNUM sold through my LHS for under 15 bucks from 3 inch and under. Not much more for bigger spinners.