7 cell nimh packs will show over 10V sometimes at full charge, but rest assured the slightest load will bring that down real fast.

Some ESC/motors can handle the extra without real problems, but others may cook right away. In my experience Novak controllers will fry with any increase past the rated limit. Castle controllers are typically underrated a bit and will hold up. But, if you are not comfortable with possibly smoking something then you should not do it. Pick up a lower Kv motor to go with your Sidewinder and you can run up to 11.1V if you like within the rated limits.