I have two old 15" cymbals, one K and one mystery (but probably K). They are both pretty heavy (1200-1500 grams).
They are both slightly warped. When held against a pane of glass, one edge bows up about 1/3".
If these were thin hi-shat cymbals I wouldn't be concerned, but I got these intending to use them as orchestral crash cymbals (either as a pair or paired with another 14" cymbal). They would be easier to play very softly if they were a bit flatter.
So, has anyone done anything to flatten a cymbal? I can flex both a little with my hands, but that certainly doesn't anything permanent. I left one bent under a desk leg for a night and that didn't do anything either.