Throttle curve on Turnigy 9x?

Does anyone use a throttle curve or expo on the throttle channel for flying a multirotor? Is it necessary?

I have a Turnigy 9x and I don't think it lets me do a throttle curve when it's in the acro mode.
 

Cyberdactyl

Misfit Multirotor Monkey
On my spectrum DX8, I use 30% expo on elev, rud and ail.

Necessary? Not really, but helps smooth things out.