I modified a few Zingers 12x4s for my Webra 50. I didn't particularly like the performance. Quicker throttle response with the modified Zinger, though not nearly the same pulling power. For now, I went back to the APC 12.25 x 3.75 for now.

I am running the modified 10x4 Zinger on a Webra 32 on my PBXL. You can go to my website under the movies link and check it out flying with the modified Zinger. You'll notice how the nose jumps up when I hit the throttle. Check them out, they will make you laugh, ecspecially the movie entitled - "OOPS!"
Enjoy - Kevin
By the way, the other movies posted were filmed right after the "OOPS!"