I took bad slippage *due* to using stop market orders which are hosted on IB's servers. I haven't taken bad slippage due to stop limits. This is why I use stop limits with a broad range (approaching the protection band) now - as IB is simply sending the same thing with a simulated stop order. The difference is my stop limit is on the exchange and will kick in much faster than it takes IB to get the current last and submit a stop limit.
Wait.... so the CME supports STOP-LIMIT orders, but not regular STOP orders (you call STOP-MARKET) ?