Setting the engine thrust so that no rudder input is needed for a vertical line is helpful. The plane should be hung like a "plumb bob" and balanced accordingly. The bigger the prop disc, the better. Low pitched props provide the easiest kind of thrust to finely control. The elevator shouldn't be "masked" by a thick airfoil. The quickest responding servos and tightest linkage will keep the pilot from having to play "catch up" with what the plane is doing. Hoverbatics is a "fad" that has rekindled my interest in sport flying, and hopefully by the time I reach age 80, I will have mastered it.

BTW, the more to the rear the CG is, the more the plane will only seem stable doing one thing, and that one thing is hovering. If a guy could devise a movable CG, then a truly stable and user friendly VTOL and horizontal flight model could be setup.