I used to do flat spins with my Four Star 40 setup with an Irvine 40 and pipe. Setup would allow me to roll about five feet on takeoff and pull straight up to what ever. The first time I tried this I gainned a lot of altitude and then entered a spin as normal. As the model decended I slowly crossed the ailerons and the model flatened out. However when I went to recover it continued to spin. After four more turns I blasted the engine and it pulled it out at around 100 feet from the ground. Scared the brown goo from my rear end. So I went back up and did it again The condition intregued me and later when flying my Astro Hog I had to try it. Sure enough, almost the samething. Fortunately both planes had more than enough power to recover from the condition and I did not loose either.

If you try it my words of advice. Have more than enough power. Start high, twice as high as normal. The first time don't let it go for more than three turns as it will make your rear pucker. Blast out with power where you would normally start a regular spin.

As another note the C/G on my 4* was around 1/2 inch back from the recommend c/g location as I wanted this model to fly my way.
The c/g on the Astro Hog was around 1/4 inch nose heavy and both models would flatten out. The Astro hog would fall straight down level when applying full rudder to blast out of the condition about 100 feet. (wish I had video)

Above all do it with a model you don't expect to survive.