CBL
What I believe that you are describing is a humpty-bump. As a previous poster (SSD?) noted there are 2 varieties - a pull humpty or a push humpty.
You will need power (all of it
) as the aircraft is so slow that you are reliant upon propwash to energise the tail surfaces. The only problem that I have encountered with these is that if I get too slow, I tend to torque roll out of them - not a major issue on a Sunday afternoon but a real penaliser in competition.
I reckon what happens is that if too slow, you run out of counteracting aileron authority and the fuselage just revolves slowly against the engine until sufficient sped has been built up on the downwards leg to restore aileron control.
In the single seat Pitts, in comps, I try and push or pull over the top at no less than 90mph - any slower and there is a very obvious hdg change and a commensurate low score!
Pull humpties are much nicer than push humpties until you have developed suitable resistance to negative G!
Hope this helps,
Stik