The Graupner Speed 6x5.5 might be one to try if you're curious about their props. The OPS .15 - which is just a perky .21 case size .15 but no monster - turned it about 24k in the air.
Not the CAM props. There are three of these that I know of: 6x5.5, 6.5x6.5, 7x7. For club 20 racing?