As a pilot I really don't care whats going on at the back be it plus or minus or for that matter where the center of pressure is at various speeds. The engineers sort that out in the design and flight envelope specifying what I can and can't do.
Longitudinal static stability does not have to be 'rocket science' when viewed in simple terms. The wing's center of lift is behind the center of gravity in cruise. A tail down force balances the resulting nose down moment. When the aircraft slows, the nose is raised which (if you look at a typical wing section) makes the top of the wing effectively more cambered, producing more lift at a given speed. Its also fairly obvious (when you look) that the wing's center of lift will simultaneously move forward, which is closer to the center of gravity. This would reduce the nose down tendency of the aircraft at reduced speed, an unstable and undesirable characteristic, but happily since the horizontal tail has a negative angle of attack in level flight, and is fixed in relation the the wing by the fuselage, its down force goes away as the wing's angle of attack increases. The designer arranges for the pitch stable effect at the tail to be greater than the destabilizing effect of the wing's center of pressure shift and as a result, you have to increase the tail down force with some up elevator/stick deflection in order to fly slower.
As long as the tail's nose down moment increases faster with angle of attack than the reduction of the wing's nose down moment, the plane has static pitch stability. At high angles of attack the wing's center of pressure moves forward of the CG, but by now the tail has transitioned to producing lift by virtue of the aircraft's increased nose up attitude (relative to the flow of air around it), so static stability is maintained.
A canard aircraft is different in that both wings produce lift at all times and the CG is located between them. Static stability is maintained by making the rear wing gain lift with angle of attack faster than the front wing (higher
dCl/
dAlpha in the obtuse vernacular
) That's why when you look at the section of a canard's front wing, it is so uniformly round on top - so it is relatively insensitive to angle of attack. To maintain lower speed, you increase the front wing's lift by pulling the stick back, deflecting what amounts to flaps on the forward wing. The good news about canard aircraft is that both wings always push upward, the bad news is that the front wing section might not be quite as efficient due to its role in generating static pitch stability.