We did. We replaced the metal fixed pitch Sensenich with the new Adjustable pitch carbon fiber prop. They offer a 13" spinner only, and our RV-4 is older, and had the 12" spinner.
The 13" spinner is slightly oversized, but I always thought the 12" spinner was a bit undersized, so to my eye it's no biggie. It's only noticable at the top.
I suppose you could blend the cowl to it with some light weight fairing filler...