That would usually be the case, but that's a tiny gasser. But if that bothers you, there are other options. I will explain, but I think you'll see why the plastic spinner will be a much easier route.

First, you'll need a lathe (See?). Get a hex head bolt whatever size the prop bolt is and drill and tap a hole in the head so you can screw an aluminum spinner into it.

Or, find a stud (or grind the head off of a long bolt) and find an adapter that will fit that size stud to the screw from an aluminum spinner.