My buddy has the same set up as you do. It flies pretty good but really struggles pulling out of a hover.
We swapped out props and finally found that a 15x4 actually worked best as big as it is. What happened was he broke the prop he had on it when he landed. So the 15x4 was the only thing I had extra of. I figured it would be way to big but it works. It went from just sitting there in hover wide open to pulling out of a hover. Although it does not blast out of hover it will do it. Just on the slow side. We also was using Cool Power 30% heli fuel. It seemed to work the best out of all the combinations we tried.