Try some of the smaller Xoar wooden or nylon props a shot too. www.franktiano.com has a good selection and so does www.swanyshouse.com I believe. I have their wood 13x4 on my GP Cap-580 and it works very well. I also tried a wood 12x6 that worked great, just wanted the plane a little slower. I think I may actually like the Xoars a little better than APC & Graupners dependign on the application.

I believe Vess is making some smaller props now too.

Believe it or not some of the Turnigy & other low-cost props from Hobby City seem to perform great too.