One way to make them safer is to lay up a spinner in a female mold out of Kevlar. I made two spinners out of this material. The first one is laid up over a styrofoam plug which is what I'm using now. It's light weight and flexible and is bolted to a .125" backup plate with four 3/16" bolts. The other one is the same material and is taken out of a mold. That one I haven't needed to use yet but when I try out another prop I will use it. Kevlar is light weight and ideal material for the part.
-Joe