I have a profile plane that does it great, here is what I do:

Start high, this manuever produces very little lift to keep the plane up, so it comes down like a rock.

Pull it to verticle, throttle at idle, wait for it to stop,
Right when it stops, put both sticks in the upper left corners, so full throttle, full left rudder, full down elevator, full left aileron.

You may need to move the aileron stick out a little bit depending on your throws, but try throwing the sticks to the upper left and see what you get. Let me know

Alex