Hey Carl, Dittos that you'll LOVE this plane! If your battery is not fully forward, do that first. Lighter is better here! I have to agree with above posts, 3.5" is way conservative. If you are experienced with this type of plane, you'll be fine at 4". My newest (of 3) with a OS 50sx I didn't even check the CG (I know, bad), just moved the battery all the way rearward under the servos and flew it. Hovered 2 minutes into maiden! One thing I'll say: Every one of these planes fly exactly the same!