Steel/Flying
Ghost/Water
Dragon/Steel
What I love about Steel/Flying is that, even though it can be checked, it can't get checked easily. We agreed to risking the Pokémon's survivability the moment that we picked Belly Drum as the focus of our strategy, so what we should focus on is keeping the more ubiquitous techniques from knocking out our creation, like Fighting and Ground techniques. Things like Flamethrower, Thunderbolt and Volt Switch are more often found as coverage techniques, and if we can support ourselves appropriately, we can work around it's two weaknesses. Other than that, we don't even need STABs to function, since our +6 Atk boost will outclass any STAB out there in sheer power, so it doesn't need to rely on Bullet Punch and Aerial ace as some naysayers may think when it comes to walls trying to outlast our creation.