If you simply add more lateral area up front on the model- you can get knife edge flips . no gadgets req'd . Honest.
On my blue foam Spitball - it will do a knife edge flip in roughly a 5 ft dia circle. ( well sorta a circle -)
it actually appears to be in a couple of feet but that isn't possible.
The profile models with lots of lateral area- properly laid out ,are simply amazing in the pitch flailing stuff
also they snap roll with a vengance in any attitude / speed.- something the long tailed stuff does not usually do .