Use the spinner--for two reasons--aerodynamics around the prop, and safety. I've had engines throw props before, and the spinner was the only thing that kept the prop from flying off and hurting someone. Unbelievably, it didn't even break the spinner. Had it broken the spinner, though, it would have still been money well spent!

Enlarging spinners isn't a very big deal at all. In fact, for most props on .46 sized motors, you won't have to enlarge the spinner holes at all--especially if you stay with a conventional 10 or 11 inch prop, and get a 2 1/2 inch or 2 3/4 inch spinner.