Mach tuck increases the tendency for speed exceedance and a mistrimmed stab can make recovery from the dive very difficult .. especially if the stab trim jack stalls and the pilot doesn't realise what's what.
Ain't that the truth.
The perfect upset scenario with early B707 types, especially the straight-pipe powered models, where the engines could get you high, but the wing was far above optimum, for the weight.
Not good...at all
