The pistons will simply flex for a while, then either the rings begin to lose seal as the ring lands deform, or the pin rips offf the domes.
I am no metallurgist .... but isn't a cast piston much less prone to "flex" than a forged piece ? ...... it is a harder and more "brittle" part than forged. The pin ripping off the dome IS a valid observation. But that concern could be limited by reducing the weight of the piston/pin combo.
