shaft torsion ?

Hi all,

5 foot wide gantry on a plasma cutter.

I want to run a shaft across and turn two spur gears on racks.

I am thinking about using 1/2" CRS as the shaft with the servo on it,
but then got to thinking about the shaft twisting.

Another idea is to use 1" OD steel electrical conduit to reduce the
twisting of the shaft.

I don't mind putting bearings along the length to eliminate any
whipping, but the twisting needs to be minimal.

Any ideas ?

Dave