IWB mag pouches add quite a bit more to your thickness especially with these thicker double stack mags(not bad with say a 1911). Your surefire will be similar is size once you put it into a pouch and I've found my belt doesn't go quite far enough
You might consider putting the flashlight elsewhere and running just a single IWB mag pouch to save on overall thickness IWB.
If you REALLY REALLY get to a point that you need your back up mag an ankle holster is going to be a bad choice. Bad guys rarely give a time out for mag retrieval during a gun fight. IWB or pocket is your best bet. Ditto for the light. A leather or material dual pocket mag holder will work many times with a mag and a light.
A forum community dedicated to defensive firearm owners and enthusiasts. Come join the discussion about everyday carry, optics, holsters, gunsmithing, styles, reviews, accessories, classifieds, and more!