Been advised to avoid Powerflex bushes also due to wearing the wishbones oval. This was from a very experienced guy who sets up and runs many of the Road Series and Pukka Cup Racers here in the UK. He's had a lot of trashed wishbones from them.
His advice was stock bushes or rose joint it with Cup Racer arms basically - although the rose joint option only makes real sense if doing the subframe and EE's etc.