Don't give up on that 11x5 by any means and don;t hesitate to try an 11x6. Both are great all around sport props for that engine. My only recommendation would be to try an APC once someone is confident they are through breaking props on a regular basis. It will perform a lot better than a Master Airscrew. I also recently bought a few Graupner props after seeing Minnflyer and RCKen talk about them several times. I have one on my Skybolt right now and so far, so good. I would say they are on par with the APC's, just not as readily available.

It is good to experiment with various prop sizes, pitches and deigns. What works for one plane and flying style may not work for another. Just because the manual says you can run a 12x5-6, 11x6, 10x7 or whatever, doesn't mean you have too. Run what works good for your plane and they way you like to fly. Don't forget about ground clearance either. Sometimes that will determine what prop you choose.