I was able to recreate this last night on G2 and it sorta looks like a very violent negative snap roll to me. Never tried to do it diving straight down on the real thing though but in G2 I left it gain a little speed then hit the right rudder and down elevator and it stayed pointing fairly straight down after attempting to go into a flat spin and started spinning like mad to the right. Talk about a wing stresser. If you would throw a little aileron into it in the same direction, instant snap roll but the plane would never recover until I gave it opposite rudder to end the spin.

Here is another one to try that will test the wing. You need lots of elevator and rudder travel for this one.

Fly straight and level then climb up at a 45 degree angle and chop the throttle (make sure you have plenty of altitude), right as the plane stops flying and just before it stalls jam the sticks into the corners (full power, full right rudder, full up elevator, full left aileron), if you time it right the plane will actually start spinning around the CG point in the upright position and start to look like it's flying backwards and get real violent real fast as the tail snaps around, then transition into a knife edge spin. The transition to the knife edge spin will be very violent as well as this is called a lomevack (S?) and is a very violent gyroscopic maneuver. This can also be done climbing 45 degrees, rolling to a knife edge then jamming the sticks in the opposite corners of the direction of the knife edge (meaning if you rolled to a left knife edge and are holding right rudder, the jam the throttle forward, rudder to full left, aileron to full right, and full up elevator) and it will snap then go into the lomevack (S?).

The best planes I have ever seen do this is either the Funtana 90 or the CG Ultimate and it will scare the heck out of you. I've heard of people getting it done succesfully on the Extra's and the Edge 540. I was able to get my Twist and my SSE to do it once but cannot get the timing right.

Make sure to land and check out the plane right after you get it to do it. The timing must be right for it to work and you will know when you have it. Both my Funtana and the Ultimate will kick the tail around 3 or 4 times then do the transition. Each time the tail comes snapping around it gets more violent.

In the full scale world this maneuver was known in the earlier days to loosen the engine on the mounts and beatup the pilot pretty good.