Ok - most prints say it can't be done
I've said before on these forums that I don't claim to be particularly knowledgeable about aeros, and that applies here too, so maybe I've got the wrong end of the stick. But when I did my aerobatics training, I entered and recovered from what my instructor called a "flat spin". Basically, enter a normal spin, then add power. The more power you add, the flatter the spin becomes - from the pilots perceptive, the nose was noticeably higher, almost as high as the S+L attitude.
Recovery was the "standard" spin recovery as for a normal spin, including reducing power to idle first (which is part of the normal recovery anyway).
This was in a Great Lakes bi-plane. If my memory serves me correctly, we also did the same thing in a Pitts S2B. And also if my memory serves me correctly, we did this both upright and inverted.
FFF
--------------