Well, maybe the Futaba Rep will say different, but that sounds predictably adequate to me.
The only way to test it more thoroughly would be to extend the antenna completely, have your friend watch the plane while you cycle the sticks, and start walking. Maybe you should carry a cell phone so your friend can keep in touch while you hike. If you can still see your plane when they report the first glitch, at least you will know the actual range (at ground level) of your setup. If you can't see the plane, then your radio has better range than your eyes will provide, so you'll never know when the plane crashes anyway.