youve only really got stretched tires in the back. doesnt count.
when beating the absolute piss out of a tire, stretched or not, they can pop a bead. i've done it...but chances of doing it under even highly spirited driving are very low.
i love stretched tires, but i dont fool myself into thinking theyre good for performance. chances are you'd be fine autocrossing that tire, but your grip threshold will be much lower.