In your shoes I'd be going the other way... up to an 11v lipo for more power.

However all of this depends upon the ESC you are using.

Most motors will tolerate higher voltages as long as you keep the overall wattage input within the same range.

The ESC ends up being the determining factor.

Will the one you have tolerate LiPo's, and how many cells or volts will it handle?

How many servos do you have and are you using the ESC's own BEC to power your RX and servos?

Better yet post the link to the ESC.