raideron, This is the way I do an inverted flat spin. I use maximum 3D rates EXCEPT on the ailerons, I use normal on them. And the UCD46 does them great. Go high, go slow level flight, off throttle, as the plane slows give full up elevator until nose stalls or not even quite a stall, go to the inner up corners with the sticks (full throttle, full right rudder, full down elevator, and full left aileron), this will start the flat spin than slowly add right aileron until she flattens out nicely. The amount of aileron will depend on the wind etc. Also after she starts to flatten out I reduce the throttle a little bit and slack of the rudder a little too or it will roll out. The last adjustments depend greatly on wind and your individual set up on your airplane. Using this techneque I can flat spin all of my airplanes. The start is always the same but the reductions and speed of the add of right aileron varies. That is where practice comes it. To do the inverted flat spin landing, which I'm pretty good at too, you just let her come on down!!!
Hope this helps,
Thanks,
Barry