Do you mean rpms? The Feigao motors are rated for 50000 rpms. Most motors can be pushed past the rated limits occasionally without issue, but I wouldn't continually run it beyond the limits. It will probably handle it, but better safe than sorry.
Very Nice! Plenty fast, if you ask me! More speed could be had with that set up for sure, but it will cut into your runtime. The funny thing is, that has less voltage (technincally) than your 12 cell setup and outperformed it easily! I am glad you are enjoying your setup.