Only thing I can say is try using a stronger metal. Ive got a 3 1/4" x 3 1/2 beast of a plate if you want it. It's pretty heavy, but I'm sure you could get it pretty light in a night of grindin.
It sure as hell won't bend... I got it for a go-kart project but that came apart in the end.

BTW it's STEEL. It really reacts to a 130lb neodymium magnet...