Not who you're replying to, but I use cast iron and steel on my induction stove and I've not had any warping over a period of 4 years now. One thing might be using the stove on the maximum setting? max power on an induction stove is going to be heating your pan MUCH quicker than on gas. Personally I only use settings over 8 (out of 10) for pots with water in them, not for skillets etc.