Interestingly, a rudder doesn't add much to the antics of a couple of 1/2A PBFs I've built, but it would be pretty hard to hover without one.

The YellowJacket might not have enough rudder area? I've experimented with taped on extensions to find the rudder or fin size that will do the job. Don't be bashful about cranking in lots of throw.

1/2A planes don't have the brute force to do the wild tumbling junk that .40 sized planes can do with the rudder, but it is still fun to play around with.