Englishal
I've just re-read your theory on the Pitts in a dive
You neglect to consider the influence of gravity
A Pitts, Hunter or MiG29 in a dive may well be experiencing slightly less than 1g. If weight reduces, so does lift. At zero g, weight is zero and so is lift. Fighter pilots use this effect to 'bug-out' from a fight,as there is no lift at this point, there is no lift-induced drag, hence faster acceleration
A lot of textbooks will tell you this!