If you try to step down the gyro you'll have to use stepdown on both the gain and rudder leads or better yet, remove the power (red) pin from the gain lead and step down the rudder lead. Keep in mind, most basic step downs are only .7volts they aren't a true 5.1v regulator. Align just calls thiers 5.1v because when they are used with a 2-1 which is 5.8v out, then you get 5.1 to the servo.
So a 7.4v with a diode step down will still be 6.7v