Quote from late apex:
What I mean is that if you are, say, long 20 EC contracts and short 2.5M EUR/USD, your total required margin at IB will still be the sum of the two individual required margins, last time I checked. Even though the risk at the account level is negligible.
By contrast, some of those forex market makers (which IB is not, and that's a good thing) that allow hedging will reduce your required margin in half, when you put on two opposite, offsetting trades in the same currency pair. As it should be.